I'll start with the book's most insignificant offense and work my way up.
First, a lot of lyric quotes have very minor differences from the lyrics printed in liner notes of U2 releases. A small issue, but in turn very distracting when the author is trying to sound authoritative on his subject, especially when correct lyrics are so readily available. Oh well, whatever, nevermind.
BUT...there's also a claim that Adam Clayton converted to Christianity which I couldn't find substantiated anywhere else, including the book he claims as its source (the interview with Bono book, a much better read btw).
Scripture is sometimes paraphrased in a way that makes it hard to find what he's talking about (as for the "opening of Isaiah" he quotes, I still haven't found what I'm looking for (commenters are welcome to help me out).
My most ill-at-ease feeling about this book comes from the way the theological stuff is presented. It seems that the author just wants to get it out of the way so he can get back to talking about how awesome U2 are. Especially considering the book is aimed at those "seeking God," this is a little perplexing. I, myself, am not seeking U2. I know how awesome they are. I would suspect that anyone who cares enough about them to read books about them does as well.
Speaking of reading books about U2, unless this is your first encounter with anything that's been in print in the last, I don't know, twenty years, you won't read much here you didn't already know. The book is bogged down with U2 facts that even casual fans probably know (Rattle and Hum wasn't well received by critics, Adam had a problem with booze, Bono was involved in the Jubilee campaign, blah blah blah). What's worse, is that the facts very often have nothing to do with the point he's trying to make! Presenting U2 trivia in this manner doesn't give you much credibility. I think it does the reader a disservice to not assume his or her level of familiarity with the subject. Again, if this is your first read about U2, you might disagree on the importance of including biographical details and U2 history, but the book is presented as being for those "seeking God," not U2.
If you are interested in U2 as Christians, the two other books "Walk On" and "Carry Each Other" are much better written and much more interesting. You'd do better with those.
I appreciated the U2 as icon introduction, but I do want to caution U2 fans who are actually seeking God to seek him in the Bible, and keep listening to U2. U2 are great, they've always been and always will be my favorite band. You do feel God's presence at their concerts, and I have certainly felt the Holy Spirit at work in my soul when one of Bono's lyrics strikes me in a way it never had before.
For those genuinely seeking God, though, don't look for him in U2. Look for him in his Word to us, and rejoice that such a fine group of musicians and social advocates have done the same.