I think poker books
get outdated very quickly because the game moves along at a fast pace and subtle changes take place all the time...so what could have been a good book at the time you bought it might be out of date with concepts 3 months later..
abit like getting a new iphone
...you know it will be worthless 4 weeks later when they bring out the latest one lol...never ends
for me, I just read books like 'the theory of poker' and 'poker math that matters' and get a good fundamental education from books like that. then its up to us to play lots of games and self improve by making mistakes and learning from them...training sites would be a better approach for learning too than books..because the videos on training sites are always uploaded and fresh with whats happening today..forums are good also for reviewing hands and lots of other things..
just need to keep your finger on the pulse when it comes to poker I think.