I have a weakness for books and for Teaching Company courses, and it is very easy to accumulate more of this stuff than I have shelves for.  The double-wide version of this piece fit exactly in a blank space of wall.  I was a bit afraid that with the size and weight I would find it awkward to assemble single-handed, but it went together rapidly, and before the adjustable shelves were added it was not too heavy for me to manipulate.

For my purposes, I was able to put two pair of adjustable shelves above the fixed ones and two below.  I did wish there had been a few more hole positions for the pegs -- it appeared there would have been space for three, not two, adjustable shelves in each open area, and then I would have had one more shelf for small paperback books.  (The present set-up is exactly the right size for my Teaching Company courses.)