Simple

• First book
• School primer
• 26-page children's book, perhaps
• Kindergarten book

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Abecedary \A`be*ce"da*ry\, n. A primer; the first principle or rudiment of anything. [R.] --Fuller.

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
"primer, alphabet table," mid-15c., from Medieval Latin abecedarium "an ABC book," neuter of adjective abecedarius , used as a noun, from the first four letters of the Latin alphabet. Abecedarian (adj.) is attested from 1660s.

Wiktionary Word definitions in Wiktionary
a. Referring to the alphabet; alphabetical; related to or resembling an abecedarius; abecedarian. (First attested from 1350 to 1470.) n. 1 (context rare English) The alphabet, written out in a teaching book, or carved on a wall; a primer; abecedarium. (First ...