The Open Syllabus Project presents a large amount of data about books listed on syllabuses of courses taught around the world (especially in the USA and not only about math/science).
I think that it is not possible to ensure that the presented textbooks are indeed the most adopted (or bought or sold or used or read). However, they probably are (at least) the most "officially suggested" ones.
In order to illustrate, I compiled below the top 3 textbooks for some particular searches.
Calculus, entire period, all schools:
- Calculus, James Stewart - Multiple Editions.
- Essential Calculus,
James Stewart -
Multiple Editions.
- Thomas' Calculus,
Joel Hass & Maurice D. Weir -
Multiple Editions.
Calculus, published in the last 10 years, all schools:
- Calculus,
William L. Briggs & Lyle Cochran & Bernard Gillett -
Multiple Editions.
- Calculus: Early Transcendentals,
Soo Tang Tan -
Brooks/Cole, 2010.
- Calculus for Scientists and Engineers: Early Transcendentals,
William L. Briggs -
Pearson, 2013.
Calculus, entire period, MIT:
- Multivariable Calculus,
Bruce H. Edwards & Ron Larson -
Multiple Editions.
- Calculus With Analytic Geometry,
George Finlay Simmons -
Multiple Editions.
- Calculus,
James Stewart -
Multiple Editions.
Calculus, 1990 to 1995, institutions of Colorado:
- Calculus and Analytic Geometry,
George B. Thomas -
Multiple Editions.
- Calculus,
Tom M. Apostol -
Multiple Editions.
- Calculus for Business and Economics,
Robert L. Childress -
Pearson / Prentice Hall, 1972.
Calculus, entire period, Open License/Access:
- Calculus: Early Transcendentals,
David Guichard -
Multiple Editions.
- Calculus,
Edwin Prine Herman & Gilbert Strang -
Multiple Editions.