I learned more from this book than any other I have read . Some of it might be a bit dated but the concepts are perfect for low to mid stakes mtts.
[ame="http://www.amazon.com/gp/product/0974150274/ref=pd_lpo_sbs_dp_ss_1?pf_rd_p=1944687562&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=0984143467&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=1PY0BG52VN0GYAH2V8H1"]Winning Poker Tournaments One Hand at a Time Volume I: Eric 'Rizen' Lynch, Jon 'Pearljammer' Turner, Jon 'Apestyles' Van Fleet: 9780974150277: Amazon.com: Books[/ame]
Written by some of the best online mtt players I ever played against .