@amoroso @pesco @davidgerard @cdegroot Sure. On my fairly vanilla 'Debian GNU/Linux 13 (trixie)' installation, I double-clicked and it opened in Atril (v1.26.2). It opened just fine and is quite readable - I've attached a screenshot for you showing some of the more complicated formulae. I didn't make any edits to the epub - this is the same file as it was downloaded from Lulu. It seems just fine! (There's a minor problem with the navigation on the left but it may not be specific to this epub.)