A brand-new reader needs words that follow the rules they just learned. A beautiful story full of "through" and "enough" will make them guess. Guessing feels like failing. A short decodable book lets them actually read.
Bob Books Set 1 is the plain start. Mat sat. Sam sat. It looks almost too small, and that is why it works. Hop on Pop, Sheep in a Jeep, The Foot Book, and Go, Dog. Go! add rhyme so the sounding-out feels like a game. The Cat in the Hat is the victory lap: still controlled vocabulary, and a story they are proud to have read.
Take turns by the page, not by the paragraph. Praise a word they worked out. Skip the speech about school.
Ten minutes, then a picture book you read to them. They should leave the session wanting the next tiny book, not dodging it.
Stop while they are still willing. A short win tonight makes tomorrow's tiny book easier to open. A long struggle makes the whole box look like school.