Kondo's book:


and the "Hidden Roots of Aikido" by Omiya, a Daito-ryu practitioner with some sort of connection to the Kansai based Daito-ryu groups, the largest of which is the Takumakai. Despite the title it is a Daito-ryu book.

I'd steer people to videos as well. There are lots to be found by the various different branches at:

Matthew Rogers www.spiritforging.com