Steven Pinker's new book, The sense of style: The Thinking Person's Guide to Writing in the 21st Century, is a complete joy to read.
I think my favourite bit of the book is where pedantry is debunked. Maybe this is so delightful because I run across such things almost every other day for work. It was also excellent to learn a little about the history of the English language and how all these rules came about.
Split infinitives were considered bad because they didn't exist in Latin. LATIN! Now though, things have changed and it's no longer so objectionable (because omg Latin). Other elements of previously pedentant-level criticism against certain sentence structures are also undone by taking away the foundation - that it wasn't done in Latin. Amazing.
However, some of the pedantry doesn't even have that solid a foundation - someone just said it and it became popular. Also some of the popular grammarians (eg Strunk and White) would often contradict themselves within the same guide! Basically, a lot has been learned through how people actually read, how words are used and crucially how the usage changes over time.
It can be very technical in parts, and I must confess, I didn't really get into the whole sentence tree thing. But still, I learned some genuine useful information (like whom is accusative but more importantly, it doesn't really fucking matter if you use who instead).
However, the use of comics (especially of T-Rex) is wonderful. It made it far more accessible and really hammered the home the point in most cases. Pinker had a lovely line for those who think using 'they' as a singular (instead of using he as universal singular) is basically political correctness gone mad:
"But the reaction is disingenuous. Every sentence requires a writer to grapple with tradeoffs between clarity, concision, tone, cadence, accuracy, and other values. Why should the value of not excluding women be the only one whose weight is set to zero?" P. 262.
English is inconsistent. We have many words and can use them in many combinations. Most hard and fast rules will always have an exception. I think the lesson for everyone is: write well, write with style and sometimes what you think is a rule, isn't one at all.
Mostly though, don't be a fucking grammar pedant. Or if you are, make sure you're not just passing on the grammar version of woo.