The bottom line is that Bell is promoting the idea that every single person will eventually be reconciled to God either in this life or the next. Some people will exist in some sort of "hell" both in this life and the next until God melts their heart and they accept His love. Jesus is necessary for salvation, at least in some sense. However, Bell's idea of hell and his view of how Jesus saves us might be very different from what you would consider a correct Biblical understanding.
Universalism
Bell is adamant that he is not a universalist. However, this all depends on what we mean when we use this term. This term does not have positive associations in many of the circles that Bell is still influential in and so it is understandable that he would want to distance himself from it. Bell must mean that he is not a universalist in the sense of other universalists who teach that all people will be saved despite their relationship to God, or that this salvation can come through all (or at least many) religions apart from Christ. However, the entire thrust of Love Wins is that everyone will eventually be reconciled to God, either in this life or the next. The logic that Bell presents in chapter 4, "Does God Get What God Wants" is that God always gets what He wants, and that since God wants everyone to be reconciled to Him, eventually every single person will eventually be reconciled to Him. Love wins. So, if by universalism you simply mean that every single person will eventually be reconciled to God, then yes, Rob Bell is a universalist. However, to be fair, Bell is not teaching that everyone is automatically spared from "hell" when they die, regardless of their relationship to God. He is also not teaching that Christ is unnecessary for salvation.
Hell
Bell affirms that hell is real and that many people will spend time in hell. He also affirms that there is some sort of future hell beyond this life, although not in the traditional sense. For Bell, hell starts in this life with the misery that comes from being apart from the life of God. Bell defines hell as "the very real consequences we experience when we reject the good and true and beautiful life that God has for us" (95). For example, Bell states:
"People choose to live in their own hells all the time. We do it every time we isolate ourselves, give the cold shoulder to someone who has slighted us, every time we hide knives in our words, every time we harden our hearts in defiance of what we know to be the loving, good, and right thing to do" (114).Therefore Bell's hell in the afterlife might not be all that much different than the type of "hell" he believes people live in during this life. For Bell, hell is clearly not punishment from God. He mocks the idea that God is saving us from God's anger. Hell is not punishment from God, but is more like a self-imposed "time out" whereby we force ourselves to sit in the corner and be miserable until we're ready to come to the birthday party. Eventually, everyone will warm up to God and come out of the corner. The consequences for rejecting God's love are basically self-imposed and temporary. Although the Bible uses terms like "eternal punishment" Bell attempts to argue that this should be translated as "a period of pruning" or "a time of trimming" (91). So Bell affirms some sort of future hell, but it is neither eternal nor punishment.
In his chapter on hell, Bell claims to deal with every single mention of the word hell in the Bible (69). Amazingly, despite this claim, nowhere in this chapter does Bell even mention Revelation 20:15 which states, "If anyone’s name was not found written in the book of life, he was thrown into the lake of fire." The only mention of this comes in a later chapter. Bell mentions the lake of fire, states that Revelation was written in a heavily symbolic way, and moves on (112).
Jesus Christ and the Cross
Jesus is necessary for salvation, at least in some sense, although maybe not like you would assume. Commenting on John 14:6 (“I am the way and the truth and the life. No one comes to the Father except through me") Bell writes,
"What he doesn't say is how, or when, or in what manner the mechanism functions that gets people to God through him. He doesn't even state that those coming to the Father through him will even know that they are coming exclusively through him. He simply claims that whatever God is doing in the world to know and redeem and love and restore the world is happening through him" (154). [I have to point out that Bell writes this as if this statement is detached from all the other statements about belief in the Gospel of John.]Bell is not teaching that absolutely all roads lead to God, but he does think that the road is wider than Christianity. Bell states, "He will always transcend whatever cages and labels are created to contain him, especially the one called 'Christianity'" (150). People need Jesus, however, "He is present within all cultures" (151). Bell states, "There is an energy in the world, a spark, an electricity that everything is plugged into" and that Jesus, as the creative Word of God, is "the energy that gives life to everything" (144-5). Bell leaves it open that people may be saved with an idea of "Jesus" that might be no clearer than this. As Bell states at one point, "Sometimes people use his name; other times they don't" (159).
Another question is how Christ saved us? The fifth chapter of Love Wins focuses on the importance of the cross. Over several pages Bell lists and describes many of the things that the cross is about: the end of the sacrificial system, reconciliation, justification (in some sense at least), victory over evil, and redemption (123-9). Bell is correct that the cross is about many things, but conspicuously absent from Bell's list is the idea that Jesus took our penalty as a substitute. Propitiation would imply that "the gods are angry" which of course God is not. For Bell, God does not have wrath toward sinners, but always and only love. Bell states that when Jesus spoke of "the coming wrath" and "judgment" He was referring to the wrath of the Romans if people provoked them (81). God never punishes, but only seeks to restore. In another place Bell writes:
"Many have heard the gospel framed in terms of rescue. God has to punish sinners, because God is holy, but Jesus has paid the price for our sins, and so we can have eternal life. However true or untrue that is technically or theologically, what it can do is subtly teach people that Jesus rescues us from God. Let's be very clear, then: we do not need to be rescued from God" (182).If Jesus didn't die on the cross as our substitute to satisfy God's holiness and justice, then what was the purpose of the cross? Yes, it accomplished reconciliation and redemption and other effects, but how? Why couldn't Bell's God do these things without the cross? Bell doesn't explain. The closest thing I have found to an explanation is Bell's statement that, "The resurrection of Jesus inaugurates a new creation" (133). This statement comes after a long description of the mysterious death-to-life pattern embedded in fabric of creation. Jesus died so he could rise and inaugurate a new creation . . . whatever that means.
In Conclusion
There is much more that could be said, but I would like to keep this a thumbnail sketch. If this were intended to be a critique, I would have included many reasons why the views Bell is promoting are in error. In a perfect world Christians would be well grounded enough in the Word of God that these errors would be self-apparent once they understood Bell's position. Sadly, this is not the case. May God use Rob Bell's book to drive Christians to the Scriptures.
Bell is right when he states that the bigger issue behind all of this is the question "What is God like?" May we look to the Bible to see all that God has revealed to us about Himself. When that happens, we will see that the Love that wins in the end is God's holy and just love. God is love, and He does win in the end--although not as Bell presents it. Because of that, I don't even want to concede to Bell the title of his book. What Bell describes as "love" is a distortion of man. A more accurate title for Bell's book would be Sentimentality Wins.