I got this as a desktop music stand but I find it also useful as a book easel and for supporting notes whenever my hands are busy.
By holding the pages up, the content is easier to read (important if you're sightreading while playing) and the stand takes up less desk space than the pages would do laid flat.
The draught of someone walking close by or opening a door can cause pages to flutter and sometimes fall off. Single sheets of paper can be secured with magnets. (I use some specifically designed for music stands.)
For books, to keep the pages open flat, I use an elastic nylon cord gadget that clips onto the upper arms of a music stand. It's not perfect, but it works.
When collapsed, it's so small & tidy that it will fit in practically any kit bag. It's a lot lighter than a regular music stand.
To open it, the back leg needs to first be pulled back from the rest of the stand. Then simply pull the "concertina" front supports to the desired width. To collapse, do the reverse. (It's well made, but you could strain and buckle it if you don't operate it like this and force it.)