What does “if” mean here? “... if at times depressing”

Question

I've just read a phrase in my Cambridge book which is:

It is compelling, if at times depressing.

My question is about the word if: What does it mean, in this case? Could I interpret it as: "It is so compelling that tends to be depressing"?

P.S.: In the book says that "if", in this case, introduces a negative idea.

Answer 1

The if in this sentence is roughly equivalent to however, as in

It is compelling, however, it is at times depressing.

Note: Some people might feel that however is too strong; this I believe depends on one's personal idiolect.

The Cobuild Grammar (section 8.72) calls this construction a concessive clause.

In general, the if in that construction implies reservation, as for example:

Many libraries have little if any control over their patrons.

or introduces a contrast as in

she was honest, if a little brutal’

Other synonyms (which can be used instead of if in this context) are

• although
• albeit
• but
• even though
• even if
• despite being
• in spite of being
• yet
• whilst

(Source: Lexico Dictionary)

So the second clause is a limitation/restriction on the first one. Whatever is compelling, is also sometimes depressing, and that might want you to argue against it.

Answer 2

If is used in that case more like a version of "although" or "even though":

if conj
2. Although possibly; even though: It is a handsome if useless trinket.
_{TFD Online}

Pay special attention to the robust usage note there.