Which book to buy depends on what you want to do or are able to do. The most common book is the TM 9-803, 9-1803A and B, if you are going to be doing maintenance and repairs yourself this is certainly the one to get.
You might also consider the electronic version as well! It is so very important to own these manuals because they tell you the basics of what you need to know. What grade oil to use? How do you service the brakes?
If you are not mechanically inclined or understand the wartime technologies you might be interested in the following two books:
Army Jill recommends that if you don’t know how to polarize your generator or have questions on how to trouble shoot various parts of your vehicle that you consider purchasing:
Automotive Trouble Shooting For WW2 Vehicles, Volume 1
Synopsis: Automotive Trouble Shooting For World War Two Wheeled Vehicles, Volume 1, is a useful manual for anyone. Do you know what to do when the cranking motor will not crank the engine? Engine fails to start? No spark? Misfiring at high speeds or under full load? Problems with your battery or battery cables? Do you know how to adjust your breaker points? Inspect the coil? Do you know how to polarize the generator? Use a jump wire to test your main light switch? Adjust your headlights? Trouble shoot your carburetor or fuel pump? All these and much more are covered. Put a copy in your truck for those little roadside emergencies!
Automotive Trouble Shooting For WW2 Wheeled Vehicles, Volume 2
Synopsis: Automotive Trouble Shooting For World War Two Wheeled Vehicles, Volume 2, is a useful manual for anyone and it takes off where volume one ended! Learn about the engine oil system. Do you know what to look for when rebuilding a block? Problems with valves? Find out how to trouble shoot and adjust the valves for wheeled vehicles. Problems with the clutch rattling? Check this manual out! Worried about your transmission or transfer case making noises? Check out the trouble shooting section. Any noises coming from your propeller shafts, universal joints or axles? Its discussed here. Trouble shooting the wheels, hubs, and rims? Chassis. Steering. Do you have brake problems, including Hydro-vac brakes? Its all here and much more. Put a copy in your WW2 truck for those little roadside emergencies! Originally produced by the US Govt, Ordnance School, Aberdeen Proving Ground, August, 1945.Edited by Robert Notman
Buy the parts book ‘Ordnance Catalog SNL – G503, 1944’. There are several other WW2 parts books available but that one is a good start. Why do you need this one? Well, it contains a lot of pictures of the parts so that you can see either what you need to fix. Sometimes it is helpful in figuring out how the pieces go back together! See here for more!
‘All American Wonder” vol I & II and this will give you the tear down and build up sequences. These were the granddaddy books of the jeep restoration “movement”. Ray Cowdery did us all a huge service for putting this information together. When some of us started on are jeeps these were not available and when they become available it was like manna from heaven.
Ren’s book, The WWII Jeep Guidebook is likely the best book to have prior to either buying the jeep (not your case of course) or beginning a restoration. While the AA1 2 and even 3 are wonderful books, I wouldn’t call them restoration guides. More like restoration hints complete with wonderful gems of information and landmines! Forget not having your oil filter connected, bad advice.
You can always ask a lot of questions on the G503.com but you really need some basic manuals to fully understand the jeep. Here is some additional advice based on Iowa’s (a G503 reader/poster) comments: Jeep Advice.