I wrote "Du schreibst ein Buch mir" and it was wrong.
Is this incorrect? Does word order matter?
Yes, word order matters.
Why not?: Du schreibst mir einem Buch
You need to use the accusative case. "einem Buch" is dative.
What is the translation for "Du schreibst mich ein Buch" into english, please?
"Du schreibst mich ein Buch" is ungrammatical.
Schreibst is dative?
Schreiben is the verb, it can't be in dative.
Why is it "mir" (to me) rather than accusative "mich"? I was thinking that a "für" is implied, like "writing a book for me".
"mich" is something like 'me' in "pick me (for the team)" in English, and "mir" is like 'me' in "give me (a kiss)"