My son is 2 and bilingual.
In his other language we have a series of books called documentary books on a particular subject, so "castles", "the sea", "the forest", "firefighters" etc.
His favourite one is about cars, and the book covers topics such as how car companies design a new car, the manufacturing process, buying cars, the motorway, accidents, filling up with petrol, Formula One etc. So these books are really quite detailed, not like picture books at all, and probably aimed at kids aged about 4-7 rather than toddlers, but my son loves them and is learning huge amounts of vocabulary.
Is there anything similar to this series in English?