Ive just been thru this with my ds who's now 4.5. He's still not keen on reading chapter books to himself and is in a phase of wanting me to read to him everything (i can sometimes get him to read page for page with me but that's about it).

We did Henry & Mudge, Nate the Great (olivia sharp is his girl counterpart), Geronimo Stilton, Tashi. He also has read some picture books. Seuss books are good as they're looooooong but not many sentences on a page usually. Eric Carle books are also good. I dont know if they're available in the US but here in Australia we have Solo readers/chapter books which are about the same level as Henry & Mudge. Zac Power also has some easy chapter books.