I have compiled an introductory book that I was happy to read when developing with Rails, but the first is to read the official documentation. However, I think that it is often difficult to understand the official documents alone. I hope it will be helpful to such people.
Ruby ・ Introduction to Ruby for professionals From language specifications to test-driven development and debugging techniques https://www.amazon.co.jp/%E3%83%97%E3%83%AD%E3%82%92%E7%9B%AE%E6%8C%87%E3%81%99%E4%BA%BA%E3%81%AE%E3%81%9F%E3%82%81%E3%81%AERuby%E5%85%A5%E9%96%80-%E8%A8%80%E8%AA%9E%E4%BB%95%E6%A7%98%E3%81%8B%E3%82%89%E3%83%86%E3%82%B9%E3%83%88%E9%A7%86%E5%8B%95%E9%96%8B%E7%99%BA%E3%83%BB%E3%83%87%E3%83%90%E3%83%83%E3%82%B0%E6%8A%80%E6%B3%95%E3%81%BE%E3%81%A7-Software-Design-plus%E3%82%B7%E3%83%AA%E3%83%BC%E3%82%BA/dp/4774193976/ref=sr_1_5?__mk_ja_JP=%E3%82%AB%E3%82%BF%E3%82%AB%E3%83%8A&dchild=1&keywords=ruby&qid=1600388138&sr=8-5
・ Metaprogramming Ruby https://www.amazon.co.jp/%E3%83%A1%E3%82%BF%E3%83%97%E3%83%AD%E3%82%B0%E3%83%A9%E3%83%9F%E3%83%B3%E3%82%B0Ruby-%E7%AC%AC2%E7%89%88-Paolo-Perrotta/dp/4873117437/ref=sr_1_1?__mk_ja_JP=%E3%82%AB%E3%82%BF%E3%82%AB%E3%83%8A&dchild=1&keywords=ruby+%E3%83%A1%E3%82%BF&qid=1600388179&sr=8-1
Ruby on Rails ・ Perfect Ruby on Rails https://www.amazon.co.jp/%E3%83%91%E3%83%BC%E3%83%95%E3%82%A7%E3%82%AF%E3%83%88-Ruby-Rails-%E3%80%90%E5%A2%97%E8%A3%9C%E6%94%B9%E8%A8%82%E7%89%88%E3%80%91-Perfect/dp/4297114623/ref=sr_1_6?__mk_ja_JP=%E3%82%AB%E3%82%BF%E3%82%AB%E3%83%8A&dchild=1&keywords=rails&qid=1600388204&sr=8-6
Rspec · Everyday Rails-Introduction to Rails Testing with RSpec https://leanpub.com/everydayrailsrspec-jp
・ Effective Testing with RSpec 3 https://www.amazon.co.jp/Effective-Testing-RSpec-Confidence-English-ebook/dp/B076VTMTV8/ref=sr_1_6?__mk_ja_JP=%E3%82%AB%E3%82%BF%E3%82%AB%E3%83%8A&dchild=1&keywords=rspec&qid=1600388276&sr=8-6
React ・ Quick learning React https://www.amazon.co.jp/%E9%80%9F%E7%BF%92-React-%E9%80%9F%E7%BF%92%E3%82%B7%E3%83%AA%E3%83%BC%E3%82%BA-%E5%B1%B1%E7%94%B0%E7%A5%A5%E5%AF%9B-ebook/dp/B07GWFRCR1/ref=sr_1_6?__mk_ja_JP=%E3%82%AB%E3%82%BF%E3%82%AB%E3%83%8A&dchild=1&keywords=react&qid=1600389000&sr=8-6 ・ Riact! React development that is not painful to start with TypeScript 3rd edition [I. Language / Environment] https://booth.pm/ja/items/2368045 ・ Riact! React development that is not painful to start with TypeScript 3rd edition [II. React basics] https://booth.pm/ja/items/2368019 ・ Riact! React development that is not painful to start with TypeScript 3rd edition [Ⅲ. React application] https://booth.pm/ja/items/2367992
jQuery ・ Introduction to jQuery https://www.amazon.co.jp/%E6%94%B9%E8%A8%82%E6%96%B0%E7%89%88jQuery%E6%9C%AC%E6%A0%BC%E5%85%A5%E9%96%80-%E6%B2%96%E6%9E%97%E6%AD%A3%E7%B4%80-ebook/dp/B00MPDUSLG/ref=sr_1_10?__mk_ja_JP=%E3%82%AB%E3%82%BF%E3%82%AB%E3%83%8A&dchild=1&keywords=jQuery&qid=1600388424&sr=8-10
BootStrap · Bootstrap 4 front-end development textbook https://www.amazon.co.jp/Bootstrap-4-%E3%83%95%E3%83%AD%E3%83%B3%E3%83%88%E3%82%A8%E3%83%B3%E3%83%89%E9%96%8B%E7%99%BA%E3%81%AE%E6%95%99%E7%A7%91%E6%9B%B8-%E5%AE%AE%E6%9C%AC-%E9%BA%BB%E7%9F%A2/dp/4297100207/ref=sr_1_5?__mk_ja_JP=%E3%82%AB%E3%82%BF%E3%82%AB%E3%83%8A&dchild=1&keywords=bootstrap&qid=1600388388&sr=8-5
webpack ・ Quick learning webpack https://www.amazon.co.jp/%E9%80%9F%E7%BF%92webpack-%E9%80%9F%E7%BF%92%E3%82%B7%E3%83%AA%E3%83%BC%E3%82%BA-%E5%B1%B1%E7%94%B0%E7%A5%A5%E5%AF%9B-ebook/dp/B07CQLGGP9/ref=sr_1_6?__mk_ja_JP=%E3%82%AB%E3%82%BF%E3%82%AB%E3%83%8A&dchild=1&keywords=webpack&qid=1600388657&sr=8-6