For a basic foundation on NLHE Tournament play, check out "Harrington On Hold'em Vol 1 & 2" (seriously don't bother with vol.3)
And for Sit'nGoes as has already been mentioned, Collin Moshmann SNG Strategy and also "Phil Shaw's SNG book".
You can likely get these at your local library. If they don't have them on the shelf, ask them for an inter-library book loan.
If you feel you're more advanced than these books, send me a pm for some more suggestions or ask here in this thread & I'd be happy to answer you.
gl & welcome to Cardschat!