I usually start lying on my belly. When my back starts to get sore, I move to my side or sit up.
Lying down on my left side. Otherwise, on my back, propped with a couple pillows.
Robin
On my side, with the book edge resting against the pillow, on my back with the book resting against my chest [NOT propped up with pillows] or on my belly with my arms holding up my head, the book in front resting on my pillow.
I generally prefer not to be sitting up or to be propped up while reading in bed, it’s just highly uncomfortable.
On my tummy with a nice perfumed pillow underneath my chin. 
Lying on my left side, head propped up with several pillows.
It’s good to know I am not a freak, and that others read the same way as I do.
But, who knew!? The side readers outnumber both my style and the “Brady” style.
Depends on the size of the book I’m reading and whether it’s hard or soft cover. If hardcover and large, I read on my stomach with the book propped up against the wall for easy page-turnage, correct page distance, and relief of arm pain or numbness. When it’s a small paperback, I can do it in any old position, but more often on my side with my head propped up with pillows.
I typically read for quite a bit longer than half an hour before bed. I own no pillows so there for make do with my arms and hands. I usually start out leaning on my right hand while reading until my wrist starts hurting. I then switch to left wrist, then stomach with my elbows tucked under me at a 45 degree angle. Shampoo rinse repeat until sleepy.
I do not recall ever reading while laying on my back, and sitting up is NO way to enjoy a good book.
Brady style, with an option for side-reading.
Brady-style, kind of. Ideally I like to build a nest of pillows and blankets and snuggle in, slouching but sitting up, with my legs drawn up and my book propped against my legs. Ahhh, perfection…
I can’t lay on my belly & read for very long, I get sore all over, and I tend to flop over and fall asleep.
stomach
Brady, with the important addition of my cat on my lap.
On my side with my head propped up by one arm and my other arm holding the book. When my wrist gets sore from holding ym head, I switch sides.
Eventually this just degenerates into me lying down with my head resting in the crook of my elbow and me reading the book sideays which my Mum gets freaked out about beacause she reckons it causes short sightedness so I am pretty neurotic about reading in that position so I usually fall asleep.