I haven't seen the printed version of this book, but it must be huge. This books covers a lot of topics in depth and you can regard it as a complement to the online Wikipedia pages or the Mathworld pages on the same subjects. I'm very happy with it, but I can't say that I've read the whole thing. It's a reference: very few people will ever read the whole thing.<br><br>I'm an ex-math major picking his way through Galois Theory thirty years after graduation (and I wander into a lot of other topics, too). That's what I use this for. It would be interesting to hear what some research mathematicians think of it.