他是前天写来的信。

[Kenny同志]

Does it mean "he wrote to me the day before yesterday" ?

Also this one: 他是刚打来的电话。

Is it: "He just gave me a phone call" ?

This sentence is perfectly acceptable （in spoken Mandarin）. Literally, it means it is a moment ago that he gave me a phone call, emphasizing the time he made the phone call. With the sentence "he just gave me a phone call", the emphasis is shifted toward the fact that he gave me a phone call.

[Zomac]

Of my grammar books that directly address the issue of using 的 with directional complements, one says:

Another book says:

Yes, i also think that 是.... 的 patten should be ended with 的.

while 他是刚打电话来的 is absolutely correct,

他是刚打来的电话 means that he's a phone call.

[renzhe]

Yes, this is what confused me.

But I guess if it's in so many grammar books, it must be correct, and I need to learn it