The Section Car Pages
Cyclopedia of Railroad Motorcars
This book differs from that of Leon in that it provides a lot more technical detail.
Yes, it does cover some of the history of speeders, but not to the same detail. There is more specific information on how the engineering of speeders evolved, the technology behind them, and why they did not change much in the last 60 years.
Illustrated with some wonderful "field photos": Paperback
May be Out of Print: I understand the Author may have died.
Keep an eye on Ebay or seond hand book sellers