Regarding the tag line, just dropping the "s" (and inserting "out" as ghostyjack said) would go a long way, "Get the most out of your reading," and "Let's get the most out of our reading together." Referring to "reading" in this general way sounds natural where referring to individual "readings" does not.
It could still use some boiling down--it's wordy and "Get the most out of" is a cliche. Maybe "Read better," and "Read better together." Or put that together as "Read better. Read together." Or stacked
Read better
Read together
There's a little confusion there as to whether "better" is talking about improving the experience or improving the skill of reading, but the confusion is lessened by tying "better" to "together," as above.