There are many wonderful music books available, including method, etude, and solo books. The list below includes several that I often use in lessons, but there are many great books not included here. I encourage more advanced students to discover new pieces on their own as well, and bring them to lessons.
Beginning Books
Rubank Elementary Method - French Horn in F or E-Flat and Mellophone
First Book of Practical Studies for French Horn by Robert Getchell
Tritons: 8 Easy Pieces for F/Eb Horn and Piano by Bram Wiggins. Hal Leonard
Canadian Brass Book of Beginning Horn Solos
Canadian Brass Book of Easy Horn Solos
The Greatest Solo Songbook – for Horn by Larry Clark. Arranged by Sandy Feldstein. Yamaha Advantage. Carl Fischer
The Really Easy Horn Book: Very first solos for horn in F with piano accompaniment. Gunning & Perason. Faber Music
Horn Solos: Book One by Arthur Campbell. Faber Music
Simple Studies for Beginner Brass: For trumpet and other treble clef brass by John Miller. Faber Music
The Really Big Student Songbook by Eric Bolvin (https://bolvinmusic.com/product/the-really-big-student-songbook/)
Classic Festival Solos (Horn in F), Volume 1, HORN BOOK (not accompaniment), Alfred Publishing
Easy Popular Movie Instrumental Solos. (Horn in F). Book & CD. Alfred Music Publishing
Rubank Intermediate Method - Horn (F, Eb Alto or Mellophone)
60 Selected Studies, By C. Kopprasch. For horn. Kalmus Edition. Studies and Technique. Published by Alfred Music Publishing (AP.K04527)
Concert and Contest Collections - French Horn (French Horn Solo Part)
The Really Big Student Songbook by Eric Bolvin (https://bolvinmusic.com/product/the-really-big-student-songbook/)
Master Solos Intermediate Level - Horn (Book/CD Pack). Edited by Linda Rutherford and Louis Stout, Sr.. Master Solos. Published by Hal Leonard (HL.841328). Louis Stout.
W.A. Mozart Horn Concertos, Schirmer edition
Morceau De Concert - Horn/Piano, By Camille Saint-Saens (1835-1921). For F horn and piano. Belwin Edition. Classical Period. Difficulty: medium. Published by Alfred Music Publishing
Advanced Books
The Art of French Horn Playing, For horn. Brass - French Horn Method or Collection; Method/Instruction. Instructional book. Published by Alfred Music Publishing (AP.0021)
60 Selected Studies, By C. Kopprasch. For horn. Kalmus Edition. Studies and Technique. Published by Alfred Music Publishing (AP.K04527)
Melodious Etudes for Trombone - Book 1, (Selected from the Vocalises of Marco Bordogni). By Joannes Rochut. For Trombone. Published by Carl Fischer (CF.O1594)
W.A. Mozart Horn Concertos, Schirmer edition
Strauss Concerto No. 1, Op. 11
Beethoven Sonata for Horn and Piano
Arthur Labar’s Orchestral Excerpts for the Horn Player.
Various etude books: Rubank Advanced Book 1 & 2, Maxime-Alphonse, Gallay, Mueller,
Solo works by Dukas, Gliere, F. Strauss, Haydn, Telemann, etc…