Well, a punctuation book. The title of the book happens to feature one of my pet peeves, so I can’t resist plugging it, even though I haven’t read the book yet.
The peeve is hyphenated compound adjectives. Or rather non-hyphenated ones. When you combine two (or more) words to modify a noun, you hyphenate them so they stay together. If you don’t, the last of the words attaches to the noun, and you can get quite a different meaning. (You can get away without the hyphen if the words form a common combination and there is no possibility of misunderstanding.) So twenty-odd means approximately twenty, but an odd duck is a person with significant personality quirks. The hyphen or lack thereof tells your reader what you mean. So give the book a read for me, would you?
Speaking of grammar books, someone recently asked me about one that mentions uncommon verb forms, such as the periphrastic that forms the title of this post. I remember Mrs. Baird, my tenth grade English teacher, made us include “to be about to” in our verb declensions, and I haven’t seen it referred to since. Maybe it was the influence of the Greek, Latin, and Sanskrit in her background. She was an odd duck…
Anyway, look for a Grammar that’s at least three inches thick. That should have it all those verb forms.