These catalogs and databases provide bibliographic information about books, as well as, in some cases, summaries and tables of contents, author information, and Japanese library holdings. They are especially useful for subject and author searches, and finding out which libraries hold books in Japan.
Several of these catalogs contain information on how to read titles and names. The National Institute of Japanese Literature OPAC gives the reading of the name of the book or journal, article title (if applicable), and author's name in katakana. CiNii Books provides a reading of the title as well as author's name. Webcat Plus (and Webcat Plus Minus) provides a reading of the title, and if author information is available on a separate page, a reading of the author name. The Tokyo University OPAC provides a reading of only the author's name. Note that while it did in the past, the new National Diet Library OPAC no longer provides any information on how to read titles or author names.
Webcat Plus is a database of Japanese books that provides a great deal of information on both books and authors. It provides both the title and author name reading for each work, as well as content summaries for some works, keywords, and related works (often irrelevant, however). For newer books, it often contains a photo of the book cover and some information from book databases.
Author pages include information from Wikipedia, photographs, brief biographical information, related people and organizations (according to Wikipedia), and a full list of the author's works contained in Webcat Plus.
It's recommended to use the 一致検索 interface for searching rather than the search on the home page of Webcat Plus; it also allows for advanced searching. The 作品検索 feature allows you to search within books for chapter and work titles, instead of by book title alone.
A guide from Tokiko Bazell at Hawaii on how to most effectively use the Union Catalog of Early Japanese Books at NIJL.