Hi kalid. That's awesome to hear you're grown the business to 3k/mo. Clearly the model of free content online + sales of curated book-length content works. Imagine now if a bunch of people with tutoring experience in chemistry, biology, economics, etc. write textbooks on their subject. Wouldn't the life of the ugrad student get suddenly better? (Stop the exploitation of ugrads! )
BTW, since you cover a lot of high school topics, you should consider making a textbook that is aligned with the common core math state standards---the big textbook publishers are scrambling to update their books right now...
Hey Ivan! Been meaning to reach out about your mini reference guides, I really like the approach. I agree on aligning with common core, I've been out of school so long I forget what old textbooks are like (the courses I have are more like "enrichment"). Well-written, reasonably-priced books that teach lasting understanding would be awesome for undergrads.
BTW, since you cover a lot of high school topics, you should consider making a textbook that is aligned with the common core math state standards---the big textbook publishers are scrambling to update their books right now...