Complex sentence: They had written compulsively from early childhood and were first published, at their own expense, in 1846 as poets under the pseudonyms Currer, Ellis and Acton Bell, and then the following year the three sisters each published a novel.
Split into simpler sentences: They had written compulsively from early childhood and were first published, at their own expense, in 1846 as poets under the pseudonyms Currer, Ellis and Acton Bell. Then the following year the three sisters each published a novel.