Best Photography Reference Website (or Book?)

I've finally purchased my first DSLR - it isn't my first SLR, I got that about 13 years ago, and it's been about 10 since I touched it - and I'm slowly remembering everything/anything that I knew before about the hands on nature of tweaking all the settings and getting the pictures the way I want them. What I'd really like though, is a source to read through and/or consult for reference.

So there's my question:

What has been the best introduction or reference that you have come across for interchangeable lens photography?

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The camera I bought was a used Pentax K-r - I chose this camera mainly for the k-mount lens compatibility but also for the affordability of used Pentax cameras.

K-r-_black_-cross-with-dal-18-55mm-bis_medium

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