Tactics book

I'm crappy so I need to work on my tactics any good book recommendations I am doing puzzles online daily and am finishing Winning chess tactics by Seirawan but I want to keep improving my tactics before I move on to improving other parts of my game any thoughts? 

The Ultimate Chess Puzzle Book by John Emms is all tactics problems. 1001 problems in all, should help. For the more advanced players, Encyclopedia of Chess Combinations (Chess Informant) is probably more challenging.

I received good advice on this forum, as I am working diligently on Tactics. 

Someone wrote that even the easy puzzles, mates in one, mates in two, forks, skewers, etc, are good to do because I can work on time, pouring through them until the patterns become instinctive.  

After finishing Chess Exam and seeing my weakness, I have ordered the Combinations 1a and 1b while working through Polgar's huge book, puzzle after puzzle, even going through the Mate in one's, just to make a thorough foundation.  There are a number of tactic books with anywhere from 300 to 1000 puzzles per (besides the Polgar book).  Besides a course of study, I am doing tactics nightly.  

I hope this helps.  Since I first read the advice about speed, several books have affirmed this practice. 

what chess exam?

I think it's this:

http://www.amazon.com/Chess-Exam-Training-Guide-Yourself/dp/0975476122/ref=sr_1_1?ie=UTF8&qid=1314601276&sr=8-1

  I just recently got "Chess Tactics For Champions" by Susan Polgar. Seems pretty good and am half way through it.  Will be going through it several times I suspect. She gives some good examples then cuts you loose on 25 - 50 puzzels per topic.

I find with my students that when you solve puzzles you should focus on the factors which made the tactic possible. Doing that helps you improve your understanding of the tactics. On this page you can learn more about what I mean - http://www.chess-strategies-tactics.com/chess-tactics/understanding-chess-tactics

why use a book? no internet access?

there are many tactics puzzles on chess.com found here.

here's another good site for tactics as well.

I had purchased a half dozen tactic books before finding the links....

General question:

when I play against a computer, I generally don't find situations for the tactics to come up.   Is this the norm?

Yes, that's the norm -- the computer is great at spotting tactics in advance, so it won't give you the chance to execute them if they can be prevented.

Humans are different.

only the basics of tactics can be learned through books ..the pin, double check, fork etc. only through the application of these ideas that transitional combinations can be allied to practical positions over the board. this can only be learned through much experiance. There is no unified theory of chess other than My System - it comes the closest and should be imediate study for those who have learned the basic mates and tactics to win material.