Complex sentence: In 1789, Fenn published two further volumes of letters, and before he died in 1794 he prepared a fifth volume for publication, which was posthumously published in 1823 by his nephew, William Frere.
Split into simpler sentences: In 1789, Fenn published two further volumes of letters. Before he died in 1794 he prepared a fifth volume for publication, which was posthumously published in 1823 by his nephew, William Frere.