Adjustability: Book support plates pivot, or 'butterfly', on hinges to hold books at any opening angle:

Left and right leg pairs can be raised and lowered, insuring that the plexiglas support plates are snug against the book covers:

Support plates also slide laterally to accommodate varying spine thicknesses:

TIP: There are two ways to adjust bookmounts for books with thick spines, or to display title pages: use the telescoping feature of the adjustable legs:

Or, use the pivot hinges to arrange the book in a deep 'V' shape:

If the 'V' you need is so deep the book wants to slip between the plates, place two lengths of 2" poly strap across the gap, taped to the plates.