Why use a leaning ladder shelf rather than a normal bookcase? The answer is style. Both do the same thing, but a leaning shelf brings in some diagonal lines to your decor. It’s a way of breaking from the horizontal and vertical lines that are dominant in most furniture. Ladder shelves also tend to be be more narrow than other shelving units, and not very tall. In the end they are shelves for displaying, more than for storing, like a regular bookshelf would be. You may not want to put heavy items on these kinds of shelves, because they are not always the most sturdy.
The two examples below are very similar and I like them both:
White leaning ladder shelves pictured:
Left: Nexxt Hadfield 5-Tier Leaning Wall Shelf, White by Nexxt by Linea
Right: White 5-tier Leaning Ladder Book Shelf by eHomeProducts
White furniture can be appealing for several reasons. It has a clean bright look, it reflects light and thus tends to brighten a room, and it is neutral and not imposing, so it fits in just about anywhere. Of course, anything white tends to get dirty relatively quickly, compared to other colors. So be prepared to dust your shelves more often than your other furniture.