You raise a good point that indicative works here, no need for subjunctive. It's disputed whether the subjunctive was used the way DL Latin teaches in this beta version. The subjunctive is almost always subsumed within a subordinate clause, as the etymology of the word indicates. Possibly the sentence fragment implies an ellipsis. On it's own this fragment can mean "May you like [i.e., have no objection to] our book." Latin usually employs a word to alert one to the subjunctive, such as ut or si, as is the case in 1 Peter 3:17, si velit voluntas Dei pati... When there's a request on its own with an object, it can take the indicative, as in Plautus' Curculio 90, voltisne olivas...? [voltis = archaic form of vultis, 2d pl indicative], "do you want some olives? = "would you like some olives?"
If it's an ellipsis with some clause missing, "you would want our book," it would need to be a 'contrary to fact' conditional with imperfect subjunctive to refer to present time, but that's not what the sentence is supposed to be doing. The creator likely conceived this sentence as a "potential subjunctive," which is a label for a type of subjunctive mood that represents the action as merely possible (an unfulfilled wish), NOT as desired (hortatory, optative) or real (indicative). Here's a link with explanation: http://dcc.dickinson.edu/grammar/latin/potential-subjunctive If there were larger context, this fragment could be a response to the question: What if the book was really good? Librum nostrum velitis, "You would want our book." In other places I've questioned whether there's sufficient evidence to posit that the subjunctive is used of polite requests, but that's a different matter.