Saintsbury introduced an edition of Donne's poems in two small volumes for the Muses' Library (Poems of John Donne, ed. E.K. Chambers, 1896, vol. I, pp. xi-xxxiii).
[Saintsbury notes how Donne's poetry evokes extreme responses for and against, making clear his own enthusiasm for Donne.]
There is hardly any, perhaps indeed there is not any, English author on whom it is so hard to keep the just mixture of personal appreciation and critical measure as it is on John Donne. It is almost necessary that those who do not like him should not like him at all; should be scarcely able to see how any decent and intelligent human creature can like him. It is almost as necessary that those who do like him should either like him so much as to speak unadvisedly with their lips, or else curb and restrain the expression of their love for fear that it should seem on that side idolatry. But these are not the only dangers. Donne is eminently of that kind which lends itself to sham liking, to coterie worship, to a false enthusiasm; and here is another weapon in the hands of the infidels, and another stumbling-block for the feet of the true believers. Yet there is always something stimulating in a subject of this kind, and a sort of temptation to attempt it.
To write anything about Donne's life, after Walton, is an attempt which should make even hardened écrivailleurs and écrivassiers nervous. That the good Izaak knew his subject and its atmosphere thoroughly; that he wrote but a very few years after Donne's own death; and that he was a writer of distinct charm, are discouraging things, but not the most discouraging. It is perhaps only those who after being familiar for years with Donne's poems, of which Walton says very little, make subsequent acquaintance with Walton's presentment of the man, who can appreciate the full awkwardness of the situation. It is the worst possible case of pereant qui ante nos. The human Donne whom Walton depicts is so exactly the poetical Donne whom we knew, that the effect is uncanny. Generally, or at least very frequently, we find the poet other than his form of verse; here we find him quite astoundingly akin to it….