For me, the most interesting selection is number 18, in which Manutius responds to the arguments of those who disparage the study of Latin.
I've also added a poem by Manutius, copied from the anthology Renaissance Latin Verse, Alessandro Perosa and John Sparrow, eds. (Chapel Hill, 1979). The poem is about the execution of Iacopo Bonfadio, a man of letters who in 1550 was charged in Genoa with the commission of unnatural acts. It is addressed to Giambattista Grimaldi, a leading citizen of Genoa and a friend and patron of Bonfadio.