I purchased 26 years upsc previous year disha publications book.
Built quality of book is also very good but sometime page quality not upto the mark.
I am the student of UPSC preparation this book is really helpful for who are preparing for competitive exam you can take idea of previous year questions paper that will help to increase your marks.
But price is little bit high but you can get a lower price on offer.
For me yes it is full value of money go for it this is my real experience it will work for you . thank you