The shelf.

LinZi covers the drills; these cover everything else. The grammar books informed our Pills; the lists inform our curriculum, all of it free or worth the shelf space.

Grammar references 语法

AllSet Chinese Grammar WikiThe best free grammar index: every point graded A1–C1 with examples, a great checklist next to our Pills.
Chinese: A Comprehensive Grammar, Yip Po-Ching & Don Rimmington (2nd ed., 2015)The reference grammar: exhaustive on complements, 把/被 sentences and clause structure.
Modern Mandarin Chinese Grammar, Claudia Ross (2nd ed., 2014)A practical guide organized by communicative function, with both scripts throughout.
Yufa! A Practical Guide to Mandarin Chinese Grammar (2nd ed., 2017)Clear pedagogical ordering with workbook exercises, good teaching sequence.