Re: This is Aikido, by Tohei
There are a couple of different editions of "This is Aikido". The original English-language edition came out in 1968, and was reprinted several times with practically no deviation until 1974. In 1975 came the first printing of the "Revised Edition", after Tohei Sensei had departed Aikikai for the Ki No Kenkyukai (Ki Society). The primary differences are a completely re-worded preface with more biographical background on O'Sensei, who had passed since the original edition of the book, and some re-titling and shuffling of topics in the "Fundamentals" chapter. "The Principle of Ki" comes to the forefront, and "Aikido Calisthenics" are now referred to as "Ki Development Exercises". Otherwise there is little difference in content or effectiveness, so don't worry that you need to get one edition or another.
This is a big book, selling for $10 US way back in the 60's. Like most of Tohei's older works, it's still a bit pricey in the used market, even though it was widely distributed back in the day. Some of the high pricing is made worse by the dozens of book dealers out there who simply haven't a clue as to the market value of things. There are guys listing used books that are only a couple of years old, and still in print and available from Barnes and Noble, etc. that are listing them literally for THOUSANDS of dollars! No kidding! So the other dealers see this, and think the book is worth a mint, and price theirs accordingly. It's a vicious circle. The best advice I can give you is shop around for a good deal, and ALWAYS offer a lesser amount than what is advertised. Ebay auctions can be a good source, particularly if an overpriced listing is near closing without any bids. Just message the dealer, tell him his book is obviously not worth what he thinks it is, and make him an offer. This book is a good edition to any serious Aikido library, regardless of your style. Happy hunting!