Textbooks for complete beginners

I’m self-learner, and I’m using Genki I (textbook and workbook). I don’t think that it’s completely unsuitable for self-learners. Many people of forums went thru Genki I and II without a class. There is a discord server dedicated to Genki for people who want to study together.

Also your post title made me think you are asking for reading materials (as in easy books to start reading), not grammar textbooks. There two master topics which will give you more than enough information to start: