How do you determine condition of a peace dollar?

If you cannot find a grading book, take a look at an auction site and find a clear picture of an uncirculated (usually graded MS60 - Mint State 60 - or higher) and look carefully at: 1) The detail of the hair on the front, and 2) the detail of the chest feathers of the Eagle on the back. If your coin has some of those details worn away, it is less than uncirculated. Grades range from "Good" - really worn, but, hey, you can tell it's a bird, to "Very Good" (VG) - you can see a few curls, to "Fine" or "Very Fine" (VF) where some/most of the details are still there to "Extra Fine" (EF) where the details are just about all there except at the high points where a bit of wear is there - they can still be very good looking coins. Plus there are various Uncirculated (MS) grades up to MS70. Some grading IS subjective.

Coin collecting (and grading is a big part of it) is a great hobby. To have a Peace Dollar of any grade is to have a piece of history. (and they do have .77 troy oz of Silver in each, btw) Good luck.