Well...I love both books and lists so this was a good oppprtunity to organize my piano related library

There may be ones that you already listed above and some of mine are in Finnish but may also be available in English. I excluded those that I am sure are not. Many are not light reading, but I love to read stuff that makes my head spin...some may also be a little controversial but reading is supposed to make you think yourself, right?
Chopin a Graded Practical Guide by Eleanor Bailie
Chopin Pianist and Teacher by Jean-Jacques Eigeldinger
Chopin's Letters by Dover Publications
The Cambridge Companion to Chopin ed. by Jim Samson
Composers on Music ed. by Josiah Fisk
Off The Record by Peres Da Costa
18th Century Keyboard Music ed. by Robert L Marshall
19th century Piano Music ed. by R.Larry Todd
20th Century PIano Music by David Burge
Practicing Perfection by Chaffin, Imreh, Crawford
The Secret Life of Musical Notation by Roberto Poli
The Art of Piano by David Dubai
A Natural History of the Piano by Stuart Isacoff
Cesar Franck His Life and Times by R.J.Stove
Eric Satie: Music, Art and Literature ed. by Caroline Potter
The Composer-Pianists Hamelin and the Eight by Robert Rimm
The Untold Story of Adele aus der Ohe by LaWayne Leno
Arturo Benedetti Michelangeli as I knew him by Lidia Kozubek
Playing the Piano for pleasure by Charles Cook
Nicolas Medtner by Barrie Martyn
Pianistic Problems by William S.Newman
The Art of Practicing by Madeline Bruser
Piano Notes by Charles Rosen
Mastering Piano Technique by Seymour Fink
What Every Pianists Needs to Know About The Body
Adaptive Strategies for Small Handed Pianists by Lora Wreal and Brenda Wristen
The Pianists Guide to Pedalling by Joseph Banowetz
The Pianists Guide to Standard Teaching and Performance Literature (A must have to adult beginners who like to choose their own pieces)
Guide to Pianist's Repertoire by Maurice Hinson (recommended only if you love to explore repertoire whether you can play it or not)
Samuel Feinberg: Pianism as Art (in Finnish)
Discussions with Horowitz by David Dubal (in Finnish)
The Memoirs of Dmitri Shostakovich (in Finnish)
Memoiries of Ashkenazy (in Finnish)
Rubinstein's self biography (in Finnish)
Chopin by Andre Gide (in Finnish)
I love Baroque Keyboard music, so I'll add these even if not from the era of the modern piano:
Domenico Scarlatti by Ralph Kirkpatrick
The Keyboard Sonatas of Domenico Scarlatti by W.Dean Sutcliffe
Domenico Scarlatti Master of Music by Malcom Boyd
Keyboard Music Before 1700 ed. by Alexander Silbiger
Francois Couperin and the French Classical Tradition by Wilfrid Mellers