noun
dictionaries and similar reference books
Refers to dictionaries as a category, often including thesauruses, encyclopedias, and other reference works. Used when talking about the collection or type of book rather than a single dictionary.
図書館の辞書類はとても充実している。
The library's collection of dictionaries and reference books is very extensive.
引っ越しのとき、辞書類をまとめて箱に詰めた。
When moving, I packed all the dictionaries and similar books together into a box.
参考書 are reference books or study guides, often for a specific subject; 辞書類 is specifically dictionaries and similar lexical reference works.
Compound of 辞書 (dictionary) and 類 (kind, category). The exact historical derivation is straightforward; the word is a modern compound.