I don't think there are textbooks on this stuff, it is too much of a niche, you probably need to read journal papers. A place to start might be the classic "Wha

I don't think there are textbooks on this stuff, it is too much of a niche, you probably need to read journal papers. A place to start might be the classic "What is liquid?" review paper by Barker and Henderson: https://link.aps.org/pdf/10.1103/RevModPhys.48.587?casa_token=-genrs8MUOYAAAAA:Fb81hNeEqpW7KS5WbVPd5NWQ5iPF_fXWyZwCcDpabL1kIcKR6HUwRiK9HeIvQaUeSBNAGt1vRn2gPE4 https://link.aps.org/pdf/10.1103/RevModPhys.48.587?casa_toke... ... and then the classic review paper on liquid crystals by Stephen and Straley: https://link.aps.org/pdf/10.1103/RevModPhys.46.617?casa_token=56_7AuMCfT0AAAAA:P_3CXKuVC_1MGFqsA-SX2dYcVqZiV1SxQ7FxFmukH73GHaLcjUMvpwffTwepIrkjzoGfmilcospc7Ic https://link.aps.org/pdf/10.1103/RevModPhys.46.617?casa_toke... But I believe the "gaping hole" as you call it has been mostly filled by the recent work. You probably still need to spend some weeks to follow along though. The motivation for my colleague was to develop the Onsager theory further, since Onsager only went to the second virial coefficient. They were able to go to higher-body contributions and get nice algebraic results for the equation of state, IIRC. I can probably dig up the DOI if you want to read it.