Thread on best books + readers to learn Sanskrit. I will list only books I have read & their pros and cons.
1. Samskrita Bharati (4 Part Series)
This is by far the best structured english course to learn to read, speak & write Sanskrit. The material is well-structured.
... and grammar is introduced at apt phases. There is enough Sanskrit text to immerse yourself & best part is they have accompanying online/in-person courses entirely in Sanskrit. This is the best method to learn spoken Sanskrit.
2. Svayam Sanskrit Shikshak (Hindi)
This is the second best immersive-learning series. There are 2 parts and progression is gradual. The advantage is it is entirely in Hindi, so the 1:1 syntax + vocab connect for native speakers is instant, Hindi being a daughter of Sanskrit.
this however is also it's only disadvantange. It's language restricted & not suitable for say a Telugu with poor Hindi or for an American or European learner. There is enough reading material here to "learn" Sanskrit.
3. The Sanskrit Language – Walter H Maurer
This is an amazing course. The best to learn Sanskrit for Americans/Europeans & an excellent one for Indians to use to learn the western grammar terminology. Best part about it? It is extremley long & has at least 100 pages of Sanskrit.