The latest edition of that encyclopedia comes out next month.
Literal
Next-month, that encyclopedia [possessive-の] latest-edition [subject-が] comes-out.
百科事典 ('encyclopedia,' literally 'hundred-subject dictionary') is a compound of 百科 ('many subjects / all fields') + 事典 ('reference dictionary'). Distinct from 辞典 ('word dictionary'). 最新版 is a compound 最新 ('latest') + 版 ('edition'). 出る ('come out') is the standard verb for publications being released.