“在线网上书店”常见的英文表达有 "online bookstore" 或 "online web bookstore"(后者中“web”稍显冗余,日常使用“online bookstore”更普遍)。
例句:I often buy books from an online bookstore.
(我经常从一家在线网上书店买书。)
This online bookstore offers a wide selection of rare editions.
(这家在线网上书店提供大量珍稀版本的书籍。)