Please yourself. And please whatever vision you have of your target readers.
No one else can make the decision that will make you happy (rich, beautiful, thin, successful beyond your wildest dreams…). Both sides of the blogging argument – ‘Never blog about yourself, only about your books’ vs. ‘Blog about what interests you, because it will attract readers to your books’ – have compelling arguments in their favor.
The important part is that these are OPINIONS, and there is no scientific way to prove one or the other, as there are writers doing it well on both sides of the argument.
By all means scan other blogs and see if you agree with the blogger’s opinions. Writing style. Choice of format. Heck, choice of background color (thin white letters on a black background drive me to the Preferences settings on my browser ’cause I can’t SEE them).
It comes down to content: can you provide what others will want to read?
If all you want is to add your bit to someone else’s thoughts – go comment on their blog posts. The disadvantage: waiting until someone else posts on the topic.
BUT: there are plenty of niches left. If, after you read for a while, you find no one ever blogs about X – you go blog about X. Instead of searching the web for solutions to your problems, solve them yourself – and post the results. Someone, somewhere, will thank you.
I write. After some six months’ reading, I have picked the Categories where I have something I want to say. They are in the sidebar. I hope there is something you may want to read.
There is enough sand in this sandbox for EVERYONE.