Here is a schematic for a 24 channel version of the ATTiny2313 servo controller. You can expand the number of channels up to the full 64 by adding additional CD74HCT238Es where each additional MUX chip is connected to the next available pin on port b. ATTiny2313-24ChannelServoController.png The schematic, in Eagle format, is here: ATTiny2313-24ChannelServoController.sch and a potential board layout is here: ATTiny2313-24ChannelServoController.brd These were produced with Eagle and I don’t think I could have worked out how to use Eagle without reading Build Your Own Printed Circuit Board by Al Williams.
So far I’ve bought three AVR programming books. AVR: An Introductory Course, Programming and Customizing the AVR Microcontroller and Atmel AVR Microcontroller Primer: Programming and Interfacing (Synthesis Lectures on Digital Circuits and Systems). They are three quite different books and each has a distinct focus. I read AVR: An Introductory Course first. It’s a slim volume that teaches you how to program the AVR family of micros with assembly language. It’s a good book and the focus is very much on learning how to program the various facilities available and how to use the various programming constructs to get work done.