Since there has been periodic comments about various tablet's functionality and convenience in reading sheet music, I thought I'd weigh in with my opinion of the Android Onyx Boox ereader. I bought 0ne about 3 weeks ago, so have had some time to form some observations. My main reason for getting it was because I'm developing cataracts and find that usual sheet music at the piano desk sight range is a bit fuzzy, even with my piano\computer\shooting glasses. I figured that the higher contrast of a display would compensate. I chose the Boox simply because it's the biggest one available, and one of the few that has the same aspect ratio as a sheet of paper, rather than a video viewing ratio. The 17 inch Samsung is too big, and awkwardly designed for use on a music desk.
The good news is it helps quit a bit visibility--wise, but not perfect. Since the E-ink dislay is not an active LED display, the contrast is not as great as I woud have liked, and does need good room lighting. It is is better than paper sheet music, and of course all my music is in one place rather than in notebooks all over. The MObilesheets Pro reader software has a Boox optimized version, and it is great. The cropping feature lets me stretch pages right to the the end of the display. The stylus notation function is great for notes and fingerings, and erasable. I particularly like the Mobilesheets half page turn function, so one can turn the page anytime you've played past halfway, and the top half of the net page is visible. ...do have to remember to turn again once you've started playing the next page. pretty damn oten I've forgotten and found myself playing thru the bottom of the prior page. So I've marked all the sheets 1A, 1B, 2A, 2B, etc. I find it's better when learning a new piece to use the full page mode, since you're staying on one page longer anyway, but YMMV of course. i did find the Mobilesheets stylus annotation function a bit wonky, it often stores the notations distorted. Mobilsheets is working on that issue however. If I want perfect notations, i use the native reader app on the Boox .
I bought a pageflip butterfly bluetooth page turner, it works great. THe mobilesheets lets you configure the pedals to do different things, so I often program the left pedal to go back to repeats, when they're not on the first page, rather the usual turn to prior page mode. The software lets you set the forward pedal to go back to the beginning when the end of piece is reached, so not having a prior page turn function is not a big issue. Of course, you can use multiple pedals and program to do all sorts of things, but for me that's overkill.
As far as the fundemental functions of the Boox go. I love it. I read a lot of kindle books, and Pdf files; I love the full size page and soft background. Battery life is great. I get 10 days between charging, and I often use it about 5 hours a day or more. There is no provision for an internal SD card. You have to get a USB-C to USB-A adapter and to use USB-A flash cards, they don't provde one. If you want use an external USB stick while using it, you need to rotate the screen 180 degrees so the USBstick is on top. The Boox has somewhere around 64 gig of internal memory, so it's not much inconvnience. YOu probably won't be storing photos and videos on it since it's monochrome, so memory shouldn't be a problem. I have hundreds of KIndle books and hundreds of Pdf magazines stored and still have 55gig free. The user's manual leaves a lot out, so you'll be poking around a lot to figure out how things work. Typical manual written by the designers instead of tech writers.
All in all, it does what it's supposed to do, and apart from preferring a brighter display, it's great.