Sorry but I have to write in Chinese.just some examples:
1.写 (verb)
写 作业.
写 信
写 日记.
2. 写作 noun usually, verb.....seldom, in some situation...
写作风格 (偏正短语)
这位作家写作并出版了一本诗集.
3. 书 as verb only in particular situation (old chinese or idioms), normaly as noun
大书特书(verb)
罄竹难书(verb)
书法 (noun)
of course and the most simple BOOK
4. 书写 much more formal than 写, but anyway..the same meanig XD.
书写工整
书写新篇章.
TO: Wozitoya
大书特书是成语哎..这真不是我的书写错误. 大写特写完全没有错,但是...如果从语文教学角度讲,这不是一个成语, 顶多是个短语.