Your original post gave no information as to whether your question about literature regarding world wide postal rates was simple curiosity or focused on a particular country or time frame.
GPU == General Postal Union, formed 1874
UPU == Universal Postal Union, formed from the GPU in 1875.
In general, prior to the GPU/UPU in 1874, all mail between the USA and any foreign countries, and between any two foreign countries, was typically governed by a separate Postal Convention negotiated and signed between the two countries. In virtually every instance, rates and procedures were unique to that agreement, and were often revised until it became necessary to simply renegotiate a new agreement.
The new UPU standardized most of the rates between countries which were members of the UPU.
Even after the GPU/UPU in 1874, the exchange of mail between UPU member nations and non-UPU member nations was complicated, and similar Postal Convention treaties were still required between many combinations of countries.
One place you might want to visit is Postal History Sunday
Each week, Rob Faux writes about one or several covers from his collection, mostly from the mid-19th century era, which were sent between the United States and Europe, and often forwarded within Europe. He discusses the sources which he uses for rates and markings, how he analyzed the markings on them, and often has links to online sources and other references to published literature that he used in his analysis. These are excellent tutorials, and there are over 100 columns available here. An excellent classroom situation.
The US Philatelic Classics Society website has some information regarding foreign mail here:https://www.uspcs.org/stamps-covers...reign-mails/
They also have links for many of the UPU Conventions executed between the United States and foreign postal administration here:https://www.uspcs.org/stamps-covers...conventions/
For Great Britain, you might check out the website of the Great Britain Philatelic Society here: https://www.gbps.org.uk/information/rates/
For France, this website has materials for the period 1848 to 1916: http://www.bourgouin-jl.fr/Tarifs%20Postaux.htm.
Google translate makes these easily understandable in English.
If you were to examine the website of any of the major dealers in philatelic literature, you should find many more publications with this information. One starting point is Leonard Hartman-The Philatelic Bibliopole
, here: http://pbbooks.com/
If you have a specific area or period of interest, please simply identify the countries and time period which are of interest and perhaps another reader can point you in the right direction. There are many experts here who understand these things much better than I do.