Pedantic, academic, scholastic, bookish are comparable as terms of derogation applied to thinkers, scholars, and learned men and their utterances.
Pedantic often implies ostentatious display of knowledge, didacticism, and stodginess. It may also connote undue attention to scholarly minutiae and small interest in significant issues.
Academic rarely carries implications of disagreeable personal characteristics but it does stress abstractness, lack of practical experience and interests, and often the inability to consider a situation realistically.
Scholastic is less fixed in its implications than the others, for sometimes the allusion is to philosophic Scholasticism and sometimes to modern education. As a rule it implies dryness, formalism, adherence to the letter, and sometimes subtlety.
Bookish often suggests learning derived from books rather than from actualities and sometimes it implies a decided literary or rhetorical quality.