Finding Spanish or Portuguese language books is not different from finding English language books. The key is using the right keywords to search your topic. Likewise, finding ebooks is not different from finding print books. Commonly in literary studies, you need to find:
Similarly, if you are looking for books about linguistics, useful sample searches are:
To make sure that you only get books results when you search the UC Library Search:
Here are more tips for searching for books:
Here are my recommended databases to search for articles (AKA as academic/scholarly/peer-review articles) for Spanish and Portuguese:
Finding Films
Finding Music: