Although a bit dated, my first recommendation is "Applying PIC18 Microcontrollers", by Barry B. Brey; Copyright 2008 by Pearson Education. ISBN-13: 978-0-13-088546-3.

Another recommendation is "PIC Microcontrollers; An Introduction to Microelectronics", by Martin Bates; Copyright 2011 by Martin Bates. ISBN: 978-0-08-096911-4.