This is the wrong way to look at it. If a textbook is bad, or is good but too difficult (i.e. bad) you will stop reading it. The alternative to self-studying a good textbook isn't studying a bad one, but studying none.
The best time to start studying mathematics was when you were 4, with multiple private tutors and supportive-yet-not-overbearing parents who are also math educators.
The second best time is right now, with whatever materials you have in front of you.
ANY textbook you sit down and read, and solve its problem sets is infinitely better than ANY textbook you don't.
Stop bike shedding and start studying!!!