What is the summary of the sonnet 'the poets' by hw longfellow?

Longfellow points out that a dead poet who is still read - is effectively alive (because people still read his poems); but a living poet no-one reads, might as well be dead (nobody notices him).

Longfellow then wonders if poetry is worthwhile.

The poem concludes by deciding that poetry is worthwhile: because the important thing about poetry is to write it, it doesn't finally matter whether anybody reads it or not (the poet already had the benefit of writing the stuff).

The notion that the point of poetry is the fun of writing it (who cares whether it is fit to be read or not?) is shared by all truly atrocious poets.