There are quite a few books out there about Linux and about embedded systems in general. Here are a few titles that you may find useful:
Considered by many as the most important Unix programming book available. If you need to understand how to think and program in the Unix mindset, this is the book you need. Stevens' books are, in general, highly recommended.
This book's style is different from most other technical books in that it uses a mix of technical explanations and practical advice about real-life issues. It captures the essence of the experiences most embedded system designers have in their day-to-day work. Jack Ganssle has regular columns in Embedded Systems Programming magazine and is a frequent speaker at embedded systems conferences.
An introductory text to embedded system design from both the hardware and the software perspective. If you are not familiar with the process of developing embedded systems, you will find this book helpful.
The classic text book for understanding how Linux device drivers are developed. Written by two respected members of the open source and free software community. A must read for any Linux device driver developer.
This book provides you with all that you need to learn how to install and use Linux without requiring any prior knowledge of either Linux or Unix. I've owned a copy of this book's first edition and have come back to it every time I forgot how something was done in Linux. A terrific book that covers much of the background material required to make the best out of the use of Linux in embedded systems.
This introductory book covers the basics of embedded software development and offers insight into many of the software tricks used in developing embedded systems.
There have been a number of books on the Linux kernel's internals over the years. This one is particularily well researched and structured, and has been updated to cover the current stable version of Linux, 2.4.