"Libro de escritura" is not either a lexía or a sinapsia. I could say "libro de física/matemáticas/...". A lexía is a compound noun (written together or not) with a full meaning (you have also compound nouns, written together or not, even with a hyphen
). I'd say that a "sinapsia" is a "lexía" with a preposition (though some authors call it "lexía compleja").
"Libro de escritura" would be what is called "sintagma preposicional", that is with a preposition (de), and it's called "complemento del nombre" because it modifies a noun.
And, of course, you can say "buen libro de escritura".
This
page explains the order of adjectives in Spanish. And
this one is about compound nouns. I've seen that there is the possibility to write the adjective before the noun in some cases (which I had never thought about before
).
I hope it helps.