I've the hardcover edition bought shortly after it came out. It's an excellent practice book for tactics education and awareness. I think of it's best value as being at hand for putting in a practice session from time to time.
Tactics are only one of many elements. I do think you'd also want to study: endgames, positional theory, and perhaps openings, too.
sftac
Most of the book is dedicated to mate in 2 problems (3412 out of the 5334); it definately is not a 'complete course' in tactics. That said, I found that after I got the book my board logic and calculation improved a lot just by 'drilling' two pages of these problems a day.
There are also some very simple endgame problems; these and the mate in 1 section are more suitable for children and absolute beginners. There is a section dedicated to miniature games which is quite fun; the games are layed out so that you can try to work out the first move of a tactical sequence from a key position.
I would definately recommend it; it is not 'instructive' in the literal sense but it is important that your learning becomes self-directed at some point. It is a great source of material for practical training exercises.
Cheers for the considered response, I'll get stuck in.
A refreshing break from straining the eggshell tracking endless notation and comment. 
Got this in a used books store for six bucks and wondered what I'd do with it. Very helpful and fun too.
General question:
is it good that the Polgar book does not have algabraic notation on each diagram? Is this something that children should be weaned off of needing?
I just got it in and wanted to use it for me and for my kids. I have been going through Polgar's "Chess Tactics for Champions" and am enjoying it.
thanks in advance,
Peter
I have already purchased chess tactics for champions and would love to have the pgn file but after many web searches, I find nothing; aidin299 where did you find it? Thanks. - Sean
I can't comment on the book because I don't own it but a good rule of thumb is to check out user reviews and ratings at www.amazon.com
Is this book a complete course in tactics? The bulk is mate in 1/2/3 problems, has someone been through enough of the book to see if doing the problems gives you a good feel for middlegame tactics? I guess forks/pins/skewers etc come up in the mate problems but whether or not you're trained for them in more complex middlegames I don't know. It would be good not to go through all those questions to find you'd need another fairly basic tactics book/program after.