....list will be quite long of relevant publications, but one or two that spring to mind off the top of my head would be CAP 371 (FTL's), CAP 393 (ANO), EU-OPS, depending on where you plan to 'control', a read through of the Eurocontrol manual regarding ATFM etc. - various other publications relating to performance considerations and flight planning, of course a lot of the last two will come down to a/c type and system used for planning.
I'm sure there are a huge number of other areas you can delve into and many more experienced guys and gals will correct me......looking and thinking about it, did i really used to be an 'Ops Controller' ?? - hmmmm......jeez, i must have been useless....ultimate respect for Ops Staff i have to say....need a patience of a saint, able to juggle umpteen things at once and still have capacity for that unexpected "curve ball" usually thrown in for good measure by an unknown source...usually the boss ! lol
F/O