An old thread suggested a couple of multivolume histories of England by Samuel Rawson Gardiner (S.R. Gardiner):
viewtopic.php?f=1&t=16583
While that looks like an interesting project that would be cool to work on, curiosity led me to Project Gutenberg to look up this author, and I found that he has several other titles that also look like they have good potential, and none of his books have yet been recorded here, so I thought I would suggest them:
The Thirty Years' War, 1618-1648 http://www.gutenberg.org/ebooks/40082
What Gunpowder Plot Was http://www.gutenberg.org/ebooks/34606
A Student's History of England, v. 1: B.C. 55-A.D. 1509 http://www.gutenberg.org/ebooks/28157
A Student's History of England, v. 2: 1509-1689 http://www.gutenberg.org/ebooks/40192
A Student's History of England v. 3: 1689-1919 (not in Gutenberg but...) https://archive.org/details/studentshistoryo03garduoft
Oliver Cromwell http://www.gutenberg.org/ebooks/45010