A very high-quality hardback edition, with thick paper, sewn binding, and fine, full-size reproductions of Blake's illustrations from the excellent Cambridge originals. Originals vary a good deal; compare these with the muddy ones used in the Oxford edition. Each illustration faces the associated poem, the only sensible layout, but something the Oxford edition does not do, for some reason. The introductory notes by Richard Holmes are brief, but extremely good.
All that's lacking are detailed explanatory notes for the individual poems, but those are available on web and elsewhere, and they aren't much needed for these poems in any case.