This second English edition of Gesenius' Grammar, edited and enlarged by the late E. Kautzsch, stands alone as the definitive reference work on Hebrew grammar. It is revised in accordance with the 28th German edition by A.E. Cowley, and includes a facsimile of the Siloam inscription.
Even though dated, it is still the most comprehensive reference grammar out there. Unfortunately, it is rooted in mid-19th century philology and understanding of language. Definitely time for a new one.