You asked about books. I downloaded three kindle books that I found very useful when I decided to take this up as a hobby. I downloaded the kindle reader app for my ipad to read these, but I think you can get a reader application for almost any device including a pc. All these can be purchased from Amazon and it'll be less than $30 for a lot of information.

Trolling Big-Water Walleyes by Chip Gross $12.95
Walleye Spinner Fishing Secrets by Mark Romanack $6.99
Walleye Tactics Crankbait Trolling by Mark Romanack 6.99

The Romanack books go into great detail about the precision trolling book which has been replaced by the app. I enjoyed all three books. Each of them discuss using planer boards, how to get to depth, boat selection and rigging, and discussions on how tactics change with the seasons. The Chip Gross book really goes into depth on the different tactics for the different seasons and it's written from a western to central Lake Erie perspective.