Its unlikely that you will find any motherboard chiplevel repair ebooks online. There are 2 books on motherboard available in India. I've got them at Bombay(Mumbai) at Lamington Road. With these you will get to know how the boards from the old 486 upto Pentium 4 boards work. The diagnosis techniques are the same even for boars that are new. For new Chips, all you need is to go through the datasheets on company websites or sites like
www.alldatasheets.com.
What's most important is that you have a strong foundation in digital and analog electronics and understand how microprocessors and microcontrollers work and how to test them. The more experience you have in testing and repairing electronic devices the better.
Mostly what fails in boards are electrolytic capacitors, MOSFETS in the power supply section, The VRM controller ICs that control the MOSFETS, the PWM ICs that give signals to the VRMs, the clock generator IC and/or its Crystal. Also obviously fuses on the board.
You need to use experience from testing other digital equipment to fix motherboards. The more you fix, the better you'll get.
Google online for "VRM testing". Start learning on dead boards. Boards with PS2 keyboard and mouse not responding faults can be due to fuses. IF both have failed, it could be the I/O controller IC. This is the fault when both PS2 ports and all USB ports are not working.
Keep practicing and with time you'll get better. For parts you need to salvage old junk boards. These you can get cheap or free from people who discard them for new ones. Every junk board has potential components for future use.
Best regards!