Fallout 2 Hintbook

The Fallout 2 hintbook is a bonus item available after finishing Fallout 2. When used, the hintbook yields 10,000 experience points and increases all skills to 300%. It can be used infinite times, for another 10,000 experience each time. Due to a bug, the SPECIAL is not maxed out, although killap's patch fixes this omission.

You can get it from Father Tully in New Reno if you continue the game after destroying the Enclave's Oil Rig.