Books on savings

Slms, if a person is writing a book on how to have certain amount of savings at a certain age. The book is aimed at all audience therefore it isnt highlighting shariah compliant savings etc and rather then using the word interest the word dividend payment is used, wil the person be sinful if the readers bought and invested in non shariah compliant shares. The book is based on passive income but no suggestions of individual shares or funds has been given just a guideline on how much a person should save.
Please kindly assist.