Donating books to city/school libraries seems like the most scalable way to donate thousands of books in an impactful way, especially over the long term since more people can read each copy

Are there a lot of EA student/university groups (or city-based meetup groups) in Russia? You could send maybe 20 copies to each local EA group, so they can have something to hand out to interested local members.

Alternatively, set up a booth at a Harry Potter convention/meetup (if such things exist)?? Harry Potter fans will be much less influential on world affairs compared to math geniuses. But they will be much more likely to read the book!

[Are kids graduating high school today likely to have read Harry Potter? Or is it mostly people in their 30s (ie, they were children while the books were coming out) who have the highest likelihood of being familiar with the series? Maybe you should target your recipients by age.]

You're targeting math students and computer scientists, presumably because they are relevant to AI safety research (plus the preexisting knowledge of HPMOR in those fields, and the fact that people with nerdy/futurist personalities are a natural fit for the book). Consider expanding your search to other fields that are relevant for 80,000 Hours career paths:

• Microbiologists and materials scientists who might be able to contribute to pandemic defense or advocate against bioweapons development

• Nuclear scientists or aerospace engineers? Although my impression is that, while these people might work on important military technology, they don't have much influence over how it is developed or ultimately used. But these people would be a good personality fit for HPMOR, and might have the same relationship to nuclear and great-power-conflict risks that computer science whiz kids have to AI risk.

• Are there some reliable routes that people take in Russia to positions of political/military/strategic influence? For instance, in the USA, I might try to target "all political science & law graduates of Ivy league schools", while in China, this might be "all Tsinghua graduates who are members of the CCP". These people probably aren't a natural fit for HPMOR's nerdy appeal, but it might be worth considering anyways.

You don't state whether the condition is that the book must get distributed inside Russia, but I think your comment about the shipping costs outside of Russia means that you are interested in international reach as well. 

I think some of the things you might do:

1) do all the steps you already did for in-country distribution (maths Olympiad winners etc) in the countries of ex-Soviet Union with a large Russian speaking population (Ukraine, Belarus, the Baltics, Georgia, Kazakhstan, other stans). 

2) Approach Russian student societies (or Rationality/EA adjacent) of (whatever selection: Ivy league, Russel group, much broader to take advantage of the large print amount) of universities, particularly with maths/rationality background and offer them the books. Even small and less prominent universities have a substantial number of Russian students/ Russian speaking students - e.g. I know University Comenius Bratislava Maths Physics Faculty has Russian students. 

3) Approach Ukrainian refugee organisations in the EU to see if they have organisations that coordinate Ukrainian high-school students in the countries and see whether they would want to take these books. For a lot of these students this would be a lot easier to read in Russian rather than English and even if an Ukrainian copy exists (I don't know if it does), there are plenty of speakers who use Russian as their first language. 
 

Suggestion: reminder somewhere here that this is Harry Potter and the Methods of Rationality