I am actually writing a master thesis in LaTeX but I didn't really like the default page style of the document style book. Therefore I tried to make my own page style and I resized manually the margins.
Now comes the question: is there a best ratio of number of letters per line (I count a space as a letter), and number of lines per page if the size of the page is a classical A4 format in order to get the text as readable as possible? Also what should be the best size of the police?
I have not really find a precise information on this subject so far. Moreover, I tried to determine for myself those ratios using books and articles, but it seems that those ratios differ widely depending on the size of the pages, on the publisher, on the author...
Actually, a page of my thesis counts between 70 and 75 letters per line (in 12pt) and between 38 and 42 lines per page. However I am not totally satisfied of those settings. On the one hand, I think that a page is too heavy to read with these settings (which maybe depends also a bit on the size of the letters), on the other hand I want a page to contain enough informations: somehow I don't want a reader to have to turn continuously the pages, since this "breaks" the reading.
I know that one could always argue that this is a subjective question, but I am almost sure that there are very accurate such ratios and that this question has already been studied scientifically.
Does anyone know a good reference for this problem?
As usual, thanks in advance!