Reddit reviews Fundamentals of Men's Fashion Design: A Guide to Casual Clothes

You will get more quality, but will not save money making trousers if your comparison is ordinary RTW.

Here's a book:
https://www.amazon.com/Fundamentals-Mens-Fashion-Design-Clothes/dp/0870055143#customerReviews

My teacher, who was the head of a Menswear program, did not teach directly from these books (he had his own approach, as many teachers do), but he recommended this book:

https://www.amazon.com/Fundamentals-Mens-Fashion-Design-Clothes/dp/0870055143/ref=cm_cr_othr_d_product_top?ie=UTF8

Here are some books on tailoring and a link to a tailoring forum:
https://www.amazon.com/Classic-Tailoring-Techniques-Construction-Collection/dp/0870054317

https://www.amazon.com/Classic-Tailoring-Techniques-Menswear-Construction/dp/1628921706/ref=pd_sim_14_3?_encoding=UTF8&pd_rd_i=1628921706&pd_rd_r=QJRZP6W10YZA3RAQVJCT&pd_rd_w=K0lmR&pd_rd_wg=MYIWi&psc=1&refRID=QJRZP6W10YZA3RAQVJCT


(Great price at $39.66)

https://www.amazon.com/s/ref=nb_sb_noss_1?url=search-alias%3Dstripbooks&field-keywords=roberto+cabrera



http://www.cutterandtailor.com/forum/index.php?showtopic=2130

This book has been recommended to me by a menswear teacher.

Fundamentals of Men's Design: A Guide to Casual Clothes.

There's a companion volume that gives drafts for more formal clothing.

New Complete Guide to Sewing for general sewing techniques.

For tailoring men's clothes, Classic Tailoring Techniques (and women's.)

For pattern drafting, Winnifred Aldrich has a great line of books.
There's also Fundamentals of Men's Fashion Design, casual and tailored. As well as Patternmaking for Fashion Design.

For corsets, Waisted Efforts and The Basics of Corset Building are good.

For making shirts, Shirtmaking.

For learning to sew stretch/knit fabrics, Sew U: Home Stretch is pretty good.

And for just having a bunch of fun with patterns, the Pattern Magic series is plain awesome. I think there's three of them out now.

Edit: thought of more!

The Art of Manipulating Fabric is great. And www.threadsmagazine.com as well as the corresponding print publication.