Maybe try some of the early chapter books that have a few pictures?

Magic School Bus has a chapter book series and usually each chapter will have a picture
the James Herriot's children treasury (they are various stories from his All Creatures Great and Small series)
Mrs Piggle-Wiggle series
Encyclopedia Brown books

otherwise, if those don't have enough pictures, you may want to look for some fairly in depth picture books like "Alex the Parrot" or "Gregor Mendel: The Friar Who Grew Peas" (I find for picture books, non-fiction picture books may be more challenging - we have a lot of those at home and even as an adult, I find them engaging and about people, animals and events I never knew about - for instance one on Charles Drew: Doctor who got the world pumped up to donate blood).

"The Princess in Black" is a good twist on the princess thing (it is a brief chapter book with pictures).

A Boy and a Jaguar by Alan Rabinowitz

Anything by Mo Willems.

My 4.5 year-old likes Shel Silverstein's Giraffe and a Half, the Magic Tree House series, the Young Cam Jansen series, and the Thea Stilton series.

A word of warning on the Magic Tree House series. My son did fine with them, but I was not prepared to discuss issues like slavery, the deaths on the titanic, the unpleasant nature of war, etc. The series gets into some heavy topics pretty quickly. All things considered, I feel like reading them was a positive experience, but not all kids would benefit from reading them this early.

And as a read aloud, he loves the Max Axiom Super Scientist series.

Wanted to add that we have recently started reading Life of Fred Apples and my son is really enjoying it. We first tried it around age 3 and he didn't like it at all. Pulled it out on a whim this week and he is really enjoying the humor and he loves the math, even though he has known the math it in for a long while. I'm just happy he's enjoying it. He loves that Fred is a 5 year-old math professor.

As read-alouds, DS3.5 loves Roald Dahl, particularly "Fantastic Mr. Fox" and "Charlie and the Chocolate Factory". (Frankly, Fantastic Mr. Fox is a bit of an obsession!)

We've also come across a series called "Body Battle" by Vicki Cobb that features electron microscope images of various cells in the body responding to colds, cavities, scraped knees, etc, which are a big hit.

Flower Fairies Friends Chapter Book series, based on Cicely Mary Barker's artwork and poetry.

The content is gentle, appropriate for very young children, and no deeper than you would expect based on the series title or concept, but the writing is significantly more sophisticated than, say, Rainbow Fairies. Many are leveled at AR grade 4, 5, or even 6.

Most/all of them are written by Pippa Le Quesne or Kay Woodward. The former author appears to write to a slightly higher reading level (late grade 5/early grade 6).

When searching for them, they may be listed under either the actual author's name, or "Cicely Mary Barker".

Here's one:

http://www.amazon.com/Willows-Underwater...ERWPGWBTCBECSD0

Adding a link to the thread on What books come after leveled readers?, which mentions a 4-year-old.

Adding a link to the thread on Kindergarten first chapter book, which mentions a 4-year-old.

Adding a link to the thread on Content appropriate chapter books for 4 year old.

Adding a link to the thread Recommend reading materials for 4 yrs old.

Adding a link to the thread Chapter books for 3 year olds.