''I am engaged to write little Lives, and little Prefaces, to a little edition of the English Poets.'' So wrote Samuel Johnson to James Boswell. Such understatement! It is difficult to believe he is writing about about what Walter Jackson Bate has described as ''one of the masterpieces in the history of both biography and literary criticism.''

The occasion for the work was humdrum enough. It was conceived as a countermove, by thirty-six leading London booksellers and publishers, to an ''invasion of what we call our Literary Property.'' In other words, a Scottish firm, the Apollo Press, were already publishing pocket-size volumes in a series called The British Poets. Samuel Johnson was recruited to provide the apparatus for the London equivalent. From the very first life - Abraham Cowley - is was clear he was going to do much more than that. Johnson was at the height of his powers, and this was a peculiarly congenial task. In all, he wrote fifty-two lives. He was paid a mere 200 guineas. He didn''t grumble saying instead, ''The fact is, not that they have paid me too little, but I have written too much.''

Of this great work T. S. Eliot wrote, ''Considering all the temptations to which one is exposed in judging contemporary writing, all the prejudices which one is tempted to indulge in judging writers of the immediately preceding generation, I view Johnson''s Lives of the Poets as a masterpiece of the judicial bench.''

Faber Finds, in the year that celebrates the 300th anniversary of Samuel Johnson''s birth, is reissuing a great work in a great edition. George Birkbeck Hill was the most celebrated nineteenth-century Samuel Johnson scholar. His edition of Boswell''s Life of Johnson may be his chef d''oeuvre but his edition of Johnson''s Lives of the Poets is not far behind it. It is a work of enduring scholarship which only recently has had to take second place to Roger Lonsdale''s magnificent edition.

Contents of Volume I: Cowley, Denham, Milton, Butler, Rochester, Roscommon, Otway, Waller, Pomfret, Dorset, Stepney, J. Philips, Walsh, Dryden.

Contents of Volume II: Smith, Duke, King, Sprat, Halifax, Parnell, Garth, Rowe, Addison, Hughes, Sheffield, Prior, Congreve, Blackmore, Fenton, Gay, Granville, Yalden, Tickell, Hammond. Somervile, Savage.

Contents of Volume III: Swift, Broome, Pope, Pitt, Thomson, Watts, A.Philips, West, Collins, Dyer, Shenstone, Young, Mallet, Akenside, Gray, Lyttelton.