Fortunately, you can now find lots of great children's books in Spanish that are perfect for shared or independent reading. The Colorín Colorado website provides a wonderful list of Recommended Books for Children. There is a brief description of each, as well as a recommended age level. You will also find links to several other sites that have either Spanish language books or books about Hispanic culture or heritage. One of these sites, for example is Críticas, an online magazine designed primarily to provide librarians with information on the latest good books in Spanish. Each month, there are several reviews of Spanish-language books for children, and you can also access an archive that has all the reviews from the past year.
Please see the list below of several publishers who also offer classroom sets of leveled "little books" in Spanish: