as much time as possible reading

你大概省略了句子的前半部分..完整的句子是：She spends as much time as possible reading.
语法：spend 多少时间（in）+ doing -----注意了吗?在doing前面有个介词in,所以后面的动词始终是doing形式 .在spend 多少时间（in）+ doing 中,in往往被省略,所以你会问,为什么后面的动词为什么是ing形式.它不是由possible决定的,而是由spend- --(in)来决定的.又如：
1 He spent six months (in) writing this book in Japan.
2 Let's spend as much time as possible (in) working on Tom's father's farm,shall we?
明白了吗?