Yup ,Florida also regularily replace their texts with new additions.Texas has the most clout because they spend the most on education($42 billion) with a large chunk of it going towards textbooks. The "Texas Essential Knowledge and Skills" (TEKS) is the committee that decides which books will get purchased .It consists of a mix of teachers and connected political insiders .
But ,Texas and other adoption states allow citizens to read the texts and submit public comment. Thus ,conservatives and Christian groups mobilize to influence the decision in Texas ;and liberal groups like Norman Lear's People for the American Way influence California's decision.
As to who writes them....they are more compiled by the publishers than authored by any single individual or group of individuals.For the most part they are generic and bland .The authors who's name appears on the text gets paid for having their name as the author . But they in fact do not write the books.
unbossed.com » Accountability; History Textbooks Receive a Failing Grade
The process described in the OP is not new .It is only newsworthy because Texas revised their standards.
Not so much that ,but the debate over history texts mirrors the so called culture wars in the country.
The changes adopted are only mildly corrective of the trend over the years for adding liberal bias into the text.
There are about 100 changes adopted by the selection board. Most of them are things like calling the westward movement of the US "expansion" instead of "imperial " ;"Free Enterprise system " replaces " capitalism" .
California has a bill going through their legislature that would bar the changes adopted in Texas from textbooks used in California . Perhaps if
progressive Massachusetts objects to the changes they will adopt California standards .. or write their own and pay the publishers to produce a text book more to their liking.