Eric Carle and Lois Ehlert have been staples in children's literature for ages. Their passings being so close is interesting, as they had other similarities in their lives. Both used collage to illustrate their books, both went from being an illustrator to also writing their own books, and both had huge success in working with Bill Martin, Jr. Both author/illustrators greatly enriched children's literature, and while they will be greatly missed, their work is sure to live on for quite some time. You may be more familiar with Eric Carle, but you have most definitely seen books of Lois Ehlert's, so I'm going to start with her.
Lois Ehlert was born November 9, 1934 in Beaver Dam, Wisconsin. From an early age, her parents encouraged her creativity, particularly making art out of found objects. After high school, Ehlert received a scholarship to the Layton School of Art. After school, she started as a children's book illustrator, but was often frustrated by not having final say in the print colors. She worked as a graphic designer for a number of years until a friend persuaded her to return to illustration, and eventually she released her first book, Growing Vegetable Soup, followed soon by Planting a Rainbow.
Over her career, Lois Ehlert created 38 books, all of which feature her collage technique. Her book Color Zoo received Caldecott Honor Book award in 1990. Perhaps her best known books, Chicka Chicka Boom Boom and Chicka Chicka 1, 2, 3 are ones she collaborated on with Bill Martin, Jr. I encourage you to check out Ehlert's autobiography, The Scraps Book, to find out more about her and her process in making art. Below are links to some of her books in the collection.
Eric Carle was born in Syracuse, New York in 1929 to German immigrants. At the age of 6 he and his parents returned to Germany, and when he was grown up he went to the Akademie der bildenden Künste (the Academy of Fine Arts) in Stuttgart. He wanted to return to America, and did so in 1952 with his portfolio and $40 in his pocket (worth approx $400 now). He soon got a job as a graphic designer at the New York Times.
His career with children's books began when Bill Martin, Jr. saw an advertisement Carle designed and asked if he'd be willing to illustrate a book he was working on. That book, Brown Bear, Brown Bear, What Do You See?, was published in 1967, and the next year Carle wrote and illustrated the book 1, 2, 3 to the Zoo. Through the course of his career, Eric Carle wrote over 70 books for children, which have sold 152 million copies worldwide - all of which have his distinctive collage illustrations.
I encourage you to check out some of the books below, or maybe try something autobiographical like Flora and Tiger: 19 Very Short Stories from My Life, which gives glimpses into his life - including living through WWII in Germany. The Art of Eric Carle also has some biographical tidbits, but also talks about his process in making art. If you'd like to try your hand at making similar art Collage Workshop for Kids from the Eric Carle Museum is a great resource on collage techniques.