Reading vs. Writing

I posted the reading list for 2010 as a separate page rather than a blog post because it seemed like it’d be easier to find that way (for me, for you, for the evil monkey that…).

I’ve only managed to finish two books this month.  I realize the month still isn’t over, but I haven’t decided yet if two books is a worthy investment of time or not.  I love to read.  I just wonder how often I’m reading for entertainment, escape, to study the craft, to procrastinate…  You know, all the reasons people read.

How do you know, for sure, when your time would be better spent writing than reading?  How do you identify when the reverse is true?