Happy moments.

It is wrapped in gentle sunlight of spring. In this time, reading a book is happiness.

Happy moments.

It is wrapped in gentle sunlight of spring, the time a book reading this is happiness.

Wrapped in the gentle sunlight of spring, reading a book. This is happiness.

~~ 

Such beautiful imagery! I changed it to a more poetic style and natural tone. Another way: 

Happiness is the time spent reading a book, wrapped in the gentle sunlight of spring.

Enjoy the sunshine! :)