I am trying to explain to non-native speakers how to use "almost." I can't formulate (a) rule(s) to follow with regard to nouns/pronouns. So far, my only ideas are that almost can be collocated only with words (or in situations) that describe measurement or comparison. However, even this seems to fail.
almost they = incorrect (no concept of measurement or comparison)
almost everyone = correct (measurement of individuals)
A platypus is almost a duck. = correct (comparison) They are almost the same. = correct (comparison) It is almost midnight. = correct (measurement of time vs. temporal adverbial) We are almost there. = correct (but spatial adverbial)
He wrote almost a book. = incorrect, although in this case "book" would be a comparison or perhaps a measurement of the written material
I am pretty much at a loss. Thanks.