If the author has interested you in the possibility of doing the other 10% of work, I would recommend the book "Traction - How any startup can achieve explosive

If the author has interested you in the possibility of doing the other 10% of work, I would recommend the book "Traction - How any startup can achieve explosive customer growth" by Weinberg and Mares. It actually suggests gaining traction at the same time as developing to ensure a constantfeedback loop. In some cases you will even want to build parts of your product to help you gain traction.I think they even mentioned alternating each week, one week dev, one week marketing, i.e. 50%.