My first choice for a book on aikido techniques would be The Way to Union with Ki by Koichi Tohei. However since it costs at least $250 USD and you need to have a Ki Society chief instructor verify your order from Japan, it's fairly hard to purchase.
A choice for a book would be This is Aikido by the same author, ISBN 0-87040-346-X. Since this is out-of-print and generally sells for $60 - $100+ USD, it is another unlikely candidate.
Personally, I think The Way to Union with Ki
is a very dissappointing book and would not recommend it to anyone at any price. In many of the technical picture sequences the camera actually changes position making it difficult for someone who is very familiar with the technique to catch what is being shown and for someone who doesn't know what is happening it would be completely impossible. Much of the description is rather terse and not nearly descriptive enough. I don't think it is possible to get this book unless you are a member of Ki Society and even then the book had a limited run. A lot of things wrong with this book and it's not even big enough or have a pretty color picture on the outside to put on a coffee table.
Not only is the older book "This is Aikido" prettier on the outside, the contents on the inside are far, far superior in presentation and style. Anyone can read that book and get some great insights on the technical side of aikido. Very much worth having to look at again and again. Comparing it to the newer book just makes one appreciate how talented the people were that constructed this book were.