Kostrovitskaya's 100 Lessons and Vaganova's books are certainly the best. Also, for those who are interested to learn where and how "it all began", highly recommended is Jean-George Noverre's "Letters on Dancing and Ballets". Noverre is generally credited to be the founder of modern ballet as we know it. The book dates from the 1760s and can be a tough read at times but definitely worth it.

www.amazon.com . . .

There are also the outstanding books by Tarasov on male technique and Serebryannikov on pas-de-deux, but I have been unable to locate them in the US. If anyone knows where one can purchase these please email me.