Complex sentence: Lappenberg's most important work is his "Geschichte von England", which deals with the history of England from the earliest times to 1154, and was published in two volumes at Hamburg in 1834-1837.
Split into simpler sentences: Lappenberg's most important work is his "Geschichte von England", which deals with the history of England from the earliest times to 1154. This work was published in two volumes at Hamburg in 1834-1837.