Guide to the pianist's repertoire / Maurice Hinson. 3rd ed.
Bloomington : Indiana University Press, c2000
MUSIC Ref ML128.P3 H5 2000
Concert piano repertoire : a manual of solo literature for artists and performers / Albert Faurot
Metuchen, NJ : Scarecrow Press, 1974
MUSIC Ref ML128.P3 F39
A guide to piano music by women composers / Pamela Youngdahl Dees
Westport, Conn. : Greenwood Press, 2002-
MUSIC Ref ML102.P5 D44 2002
Piano music in collections : an index / Rita M. Fuszek
Detroit, Mich. : Information Coordinators, 1982
MUSIC Ref ML128.P3 F87 1982
Clavier, v. 1 (1962) - v. 47 (2008) ML1.C79
Clavier companion, v. 1 (2009)- ML1.C792
The piano quarterly, no. 34 (1960) -159 (1992) ML1.P66
Piano & keyboard, no. 160 (1993)-208 (2001) ML1.P66
M - Scores
M20-39--Solo piano music
M198-213--Piano with 3+ Hands
M1010-1011, M1110-1111--Piano with orchestra and string orchestra (includes full scores and solos with piano arrangements)
ML - Music Literature
ML128.P3--Piano music: Bibliography
ML649.8-747--Books about the piano
MT - Instruction and Study
MT220-258--Methods, etudes, etc.
Piano music
Suites (Piano)
Concertos (Piano)
Concertos (Piano with string orchestra)
Piano with orchestra
...and there are lots more. Do a subject search for "piano" and see the 426 different subject headings that begin with "piano."
Piano music--Bibliography
Piano music--Discography
Piano--History
Pianists
... and lots more. Search "piano" in the library catalog and find more than 1000 books, more than 6900 recordings, and more than 18,000 scores.