书柜里放不下这本书。 这个语法是"存在的地方+存在的方式+存在的东西" 类似的还有 大门口停着一辆大卡车。 山后面升起来一大朵云。

Your friend was being generous, exceedingly generous, I must say. xD 王丽 has perfect explanations down there. And if I were to make minimal changes to your sentence and made it grammatically correct, i d say 这本书放不进书柜里。