Hi MateusVO, welcome to Pixelation!
Nice book! You've done well, it reads clearly as such. If you want to improve I'd suggest try adding some lighting to the image to give it depth. You might find this difficult with the current view of the book, you could try the book rotated so you can see the top, side and bottom.
To make it more interesting you could try a design on the front, at that size you've got plenty of room. Or maybe just a textured front, weathered edges and/or corners.
Also if you want the direct image you can right click your image on imgur and click "Copy Link Address", that should make it work with the img tags on the forum.
One last thing, when posting here, post at your sprites resolution (don't upscale). Pixelation lets you left click images to make them bigger, and it makes edits or paint overs much easier too.
I look forward to seeing more of your pixels! :
