書 is a traditional Chinese hanzi, listed here under the keyword “book”. It is built from 一 (one) and 日 (sun). It appears as a component in 1 other character in this index.
On KumiJi Glyph Explorer, open the parts search and type “one” + “sun”. 書 is among the results, together with every other character containing the same shapes.
Open 書 in the interactive kanji search
to expand every part down to its smallest pieces, add your own names and mnemonic stories,
or search for other characters by their parts.