BSNL JTO is the best Government Job for ECE and EE departments. According to last year Notification - BSNL JTO exam consists of a 3 hour objective exam, consisting of three sections – Section:1 & Section:2 contains questions from Engineering stream with 50 questions each, while Section-3 contains 20 questions on general English & GK. But date of examination is not fixed every year. Means you have to wait for its notification. So, it is better to start preparing Engineering Subjects from 3rd year and English, GK paper after notification.
There are more chances that BSNL JTO will issue its notification this year. There is no such specific book for JTO, so first you should buy Solved Previous Year Papers of BSNL JTO and then find the weak areas and then go for subject books of that area. For GK and current affairs keep reading newspaper and browsing Internet.