George S. Ledyard
Aikido and the Harmony of Nature by Mitsugi Saotome Sensei
This is a classic... this is one you can read once a year and get something new each time.
Journey to the Heart of Aikido - Linda Holiday
Newly published... this is a really wonderful book on the teachings of Motomichi Anno, the teacher who took over oversight of the Shingu dojo after Hikitsuchi Sensei passed away. Inspirational... it reminded me of why I have stayed in Aikido for almost 40 years.
Vibration and Connection - Seishiro Endo
Endo Sensei's take on why we train and how to train. Endo Sensei was a senior student of Yamaguchi Seigo Sensei. Another teacher who is serious about Aikido as a means of personal transformation. I have always found him to be thoughtful about his Aikido and he takes his own unique path which he describes in this book.
None of these books is about technique. They are all about the spiritual / philosophical underpinnings of Aikido and the why & how one trains to make Aikido a truly trans-formative practice.
A big +1... These are all excellent
choices. These writings can help the reader to experience the history, flavor and driving thoughts behind Aikido.
A choice of Gozo Shioda titles to add to the list: "Aikido Shugyo"
and "Aikido: My Spiritual Journey".
Either will do, as there is pretty much the same info in either title.