This is the 6681st most frequent Chinese word.
枯燥
Dull; boring; uninteresting.
枯燥 is used to describe the characteristic of 'the book's content' being boring and lacking in engagement.
这本书的内容非常枯燥，我很难坚持读完。
The content of this book is very boring; it's difficult for me to finish reading it.
枯燥 is used to express the feeling of 'life' becoming uninteresting due to monotony or repetition.
经过长时间重复相同的工作，他渐渐感到生活有些枯燥。
After repeating the same work for a long time, he gradually felt life becoming a bit dull.
枯燥 describes the perception of 'the class' as being unexciting yet beneficial for foundational learning.