Some years ago, I made a list of books on English spelling reform from the early 20th century at the Internet Archive. Here are a few:

Child’s First Reader (1904?)

https://archive.org/details/childsfirstreade00pitm/page/72/m...

A Plea for Alphabetic Reform (c1905)

https://archive.org/details/pleaforalphabeti00pitm/page/n3/m...

Simplified Spelling for the Use of Government Departments (1906)

https://archive.org/details/simplifiedspelli00simprich/page/...

The Problem of Spelling Reform (1906)

https://archive.org/details/problemofspellin00skearich/page/...

The Fonetic Primer Offering the Universal Alfabet and the Science of Spelling (c1907)

https://archive.org/details/foneticprimeroff00storrich/mode/...

English Spelling and Spelling Reform (1909)

https://archive.org/details/englishspellings00loun/page/n5/m...

Simplified Spelling (1911)

https://archive.org/details/cu31924027251341/page/n5/mode/2u...

Handbook of Simplified Spelling (1920)

https://archive.org/details/handbookofsimpli00simprich/page/...