On the subject of books and catalogues:
A lot of library composers - particularly of the early, orchestral tradition - were also academics. It makes a lot of sense, as you'd generally attend a music academy or conservatory to become a composer back in the day, taking studies in composition, musical direction, etc. As a 'consequence' of this, some of these composers also became authors, writing about music theory, composition or other related subjects.
If you google around a bit, you'll find that, in particular, King Palmer has a wide bibliography, authoring a few "How to"-books on composition and orchestration, as well as books about Bach, Beethoven and so on. A partial bibliography of his follows below:
King Palmer:
Bach (1935)
Granville Bantock (1947)
Teach Yourself to Compose Music (1947)
Beethoven (1948)
Teach Yourself Orchestration (1964)
The ABC of Music (1968)
The Piano (1972)
Orchestration (1973)
Compose Music (1974)
Music (1981)
King Palmer, Stephen Rhys:
The ABC of Church Music (1967)
King Palmer, Cossar Turfery:
The Musical Production: A Complete Guide for Amateurs (1953)
Similar books can be found authored by Reg Owen, "The Reg Owen Arranging Method" (1956) and Henry Baynton-Power "How to Compose Music" (1937).
In addition to this, there are a few autobiographies to be found:
Stelvio Cipriani, Pino Ammendola, Rosario M. Montesanti:
Stelvio Cipriani - Anonimo romano (2016)
John Fox:
My Musical World (2009)
Alan Hawkshaw:
The Champ: The Hawk Talks (2011)
Ennio Morricone:
Life Notes (2016)
Steve Race:
Musician at Large (1979)
This is by no means a conclusive list, mind - I'm sure there are more.
Adrian Kerridge's "Tape's Rolling: Take One" (2016) also deserves mention, of course.
A few more books about library music, or written by or about composers working extensively or tangentially in library:
Mike Carey:
Sailing By (2000) (a biography of Ronald Binge)
C.P. Lee, Andy Willis:
The Lost World Of Cliff Twemlow: The King of Manchester Exploitation Movies (2009)
Enzo Masetti:
La musica nel film (1950)
Jack Mirtle:
The Music of Billy May (1998)
Ennio Morricone, Sergio Miceli:
Composing for the Cinema (2013)
Valerio Mattioli:
Superonda: Storia segreta della musica italiana (2016)
Samuela Totti:
La libreria musicale privata di Antonino Riccardo Luciani (2014)
Apropos academic writing, I've been doing a deep dive into the life of David H. Kimball ("Peymont") as of late. For an individual seemingly so obscure, I've actually found quite a lot of details about him and his life, detailed in old journals and books. I found out he did some writing as well.
Recently picked this up, (look towards the bottom):
- bet you didn't know about that!
