There are 3 sections of books I found helpful.
1 was about sensory integration/processing (not all children who have problems with this are on the spectrum, but like 97% of children on the spectrum do) for children & for adults,
2. just about autism spectrum
3. general parenting


Books about this that are great for adults are:
The Out of sync child - explains it all, what to look for, how the child feels etc
The Out of sync child has fun - activities you can do with them to help and improve things - kind of like what to OT does but what you can do at home. But i think it is important to have a good understanding of what sensory processing is, and what areas your child is over/under sensitive (an OT can assess this)
How does your engine run - a good way of explaining their energy levels, so that you are all using the same termanology (explaining it terms fo a red/high engine and to slow it down etc)
Sensational Kids: Hope and Help for Children with Sensory Processing Disorder
Take Five!: Staying Alert at Home and School*


Books about this for children to understand how they feel are:
Arnie and His School Tools: Simple Sensory Solutions That Build Success (this one I have read which is great, the other titles below I haven't read in total, just excerpts from amazon but they also look good)
Why Does Izzy Cover Her Ears? Dealing with Sensory Overload
Squirmy Wormy: How I Learned to Help Myself

In terms of books about autism spectrum in general, the best I've read is:
1001 Great Ideas for Teaching and Raising Children with Autism or Asperger's, Revised and Expanded 2nd Edition - this just gives such an all round guide to both parents and teachers about ever aspect, from eating, sleeping, going out, school, anything & everything and how ASD can affect it, or what you can do to try and minimize and plan for things.

This other book isn't about autism spectrum, but because of it and the nature of DS personality, he is a very strong willed active child. This book I found incredible to give me parenting techniques that help defuse the situation (along with DS psychologist as a sounding board to know which ones in the book were for us and which ones weren;t)

Taming the Spirited Child: Strategies for Parenting Challenging Children Without Breaking Their Spirits

Most of these I got from Amazon as they were so much cheaper than here, but your local library might have some.

Hope that helps