Since my friend is good friends with everyone at our local Gamestop, they let him see/play a lot of games and stuff early. I went over with him yesterday and we got to look through the GTA IV strategy guide. I only skimmed through it for 5 minutes or so (I was a lot less interested in it than I thought I was), but I did pick up a few bits of info.
1. Of course (as you all know), the achievements list out on the net is real, and there's a page listing them all, but there's no section for tips on how to get them.
2. Almost the whole guide is for the story, probably 95% of it.
3. In the back is multiple pages for maps with locations of stores, stunt jumps, weapons, and hidden packages.
4. The hidden packages are "Flying Rats", aka pigeons.
5. There is NO vehicle list. I was disappointed about this.
6. There's a section describing the multiplayer games and what the host can turn on and off in them.
7. I'd say the book is a little thicker than the GTA: SA one.
Like I said, I only skimmed through it at the time, we were talking a lot so I wasn't paying too much attention to it. I'll try asking my friend if he remembers anything from it later.