how applicable and how good are they?

I read one in 2006 i think it helped for those of us who are not good at tourneys playing pros but nowadays most lower limit tournaments are already shovefests. I'd skip them personally.

I both agree with ^^^ and think that exactly b/c of this, Kill Everyone (the most recent of the 2) is a great book. It's strength is push/fold charts and understanding. KP is too basic.

Agree, KE is great.

It's important reading it to turn on your brain and understand what is
1. timeless strategy advice (payout structure pressure, shove/fold charts etc.)
2. hyperbolic talk about 2006 player pool reads (people unreasonably afraid to go bust etc.)
3. general advice about nutrition etc. which is fine but not a reason to buy the book.

Things falling into 1. are the reason to buy the book.

Watch them going through the bits falling into category (2.) to see how good players adapt to particular villains, but don't copy their conclusions, get your own reads about your own games and adapt your strategy yourself.

There is also another one in the series called Raiser's Edge, which follows KE but I didn't think I learned as much from.

KP is very informative about how to play when you have an M<10. The push/fold strategy is far from optimal in deeper stack situations.

Twoplustwo.com's own Mason Malmuth gave the book a rating of 10 out of 10. (And, no, the book wasn't published or sold by 2+2 )

KP is basically for beginner's, while KE was written for more advanced players.