Music composition

Alan Belkin. Letter to a Young Composer
Scott Jarrett, Holly Day. Music Composition For Dummies - A light overview on motives/phrases, the role of harmony and orchestration, ideal to understand something without graduating from college first. Although the book of Belkin (see below) is also approachable (the book of Schoenberg analyzing Beethoven's sonatas is less so). The companion prerequisite book on music theory for dummies also exists.

Alan Belkin. Musical Composition: Craft and Art - A modern book on composition covering topics like motive/phrase, writing for singers and players, forms. Also his YouTube channel with videos on applied harmony, counterpoint and orchestration.

William Russo. Composing music: a new approach (1983) - Gives a progressive set of exercises for paper-and-pencil composers familiar with music notation to overcome the fear of the blank page.

Peter Edwards. Write Like Mozart: An Introduction to Classical Music Composition - A six-week Coursera course that starts with four-part writing rules and goes into textures, chord substitutions, 2:1 counterpoint with examples from Mozart and Beethoven.
Building Blocks - A music theory and composition course in an online DAW from the creators of Syntorial
Art of Composing - An email course. It's also repackaged as Workbook 101 and Workbook 201. Also https://youtube.com/@artofcomposing
Edward Sarath, Music Theory though Improvisation - as a modern books like Russo's
Jorge Variego. Composing with Constraints: 100 Practical Exercises in Music Composition
https://www.amazon.com/1001-Music-Composition-Prompts-Creativity-ebook/dp/B0BQJNG86C/
https://www.staffpad.net/
https://www.reddit.com/r/musictheory/wiki/compchallenge/
🎥 Frans Absil. Music Composition Techniques
Margaret Lucy Wilkins. Creative Music Composition: The Young Composer's Voice

Also mention GCSE and A-level books: alan charlton, russell/harris, martin hinckley

Insights into composers' minds

There are autobiographies:

Then there are composers' reflections. Some are targetting laymen, eg:

Some are targetting musicians and can be either coursebooks (Rimsky-Korsakov, Schoenberg) or descriptions of one's compositional approach (Messiaen)

And then there are sketchbooks:

Samuel Adler, The Study of Orchestration. Podcast
Г. Банщиков. Законы функциональной инструментовки
Alan Belkin. Applied Orchestration
Song Hui Chon, David Huron, Dana DeVlieger. An Exploratory Study of Western Orchestration: Patterns through History
https://mtosmt.org/issues/mto.22.28.3/mto.22.28.3.mcadams.html