The issue has appeal as a combination UN and "Eco-topical." It is often the case that booklets are ignored for a while if the basic stamps are more commonly available in sheet form, and then rise later when collectors are shocked to realize that they have empty spaces in their albums where the booklets are supposed to be, and then proceed to go on a rampage.
A nation of about 9.5 million, the Republic of Belarus retains a largely state-controlled economy, although it's government has committed to gradual privatization. Important sectors include manufacturing of heavy machinery, agricultural products, and energy production and transport. Recently, the Belarusian economy has shifted into sustained high gear, along with Ukraine, Russia, and many other Commonwealth of Independent States economies. The economic boom provided by mineral wealth of Russia and other CIS nations and Belarus' key location as a transit route between the EU and Russia have enabled it to sustain this impressive growth. Annual GDP growth has averaged about 7.5% over the past 5 years.
Many of the newly independent and newly resurrected nations of Europe and Central Asia have issued popular topical sets and souvenir sheets in modest quantities, and most are currently very inexpensive. I view such issues as low-risk speculations, as only time will tell whether either the development of stamp markets within these countries or topical appeal will push them significantly higher. In a sense, they're comparable to penny stocks, but not as risky.
Those interested in learning about investing in stamps should read the Guide to Philatelic Investing ($5), available on Kindle and easily accessible from any computer.