Dystopian sci-fi book about a designer drug that takes the world by storm and gives people weird visions

A Scanner Darkly? It's an old book (1977), but was made into a movie in 2006. Plot matches your memory, but not the author or the scriptwriter. They might have released a book version of the movie inspired by the book, which would put it close to 2010.

Possibly John Kessel's Good News From Outer Space? It has the "weird, possibly religious visions" (maybe encounters with an alien/angel/devil), as well as the rise of a religious/ political group. There's also a designer viral drug that an underground group is planning to release.

Could it be Nexus by Ramez Naam? Came out in 2012, the author's Amazon page shows that this is his first novel (though he has written nonfiction before) and that he has worked as a computer scientist (though not a game designer). The plot description here involves both a new kind of "designer drug" that allows users to link minds (really some sort of computer implant, maybe nanotechnology), and apparently though it has the potential to "unite vast swaths of individuals into a rapturous gestalt of collective understanding and empathy" there's also the suggestion of oppressive governments that want to use it for nefarious mind-control purposes:

Set some thirty years into the future, the plot focuses on Kaden Lane, a neuroscience PhD candidate at the University of California, San Francisco. Kade, his lab mate Rangan Shankari, and their friends are all practitioners of a designer drug called “Nexus 3”. However, Nexus isn’t so much a drug as it is a lattice of data relays which take up residence inside a person’s mind. The Nexus nodes allow users to experience the thoughts, memories, and consciousness of other users. Adept users, such as Kade and company, can even use Nexus to manipulate the motor cortex of another Nexus user.

Were that not enough, Kade and Rangan have found a way to evolve Nexus into something which takes up permanent residence in a person’s mind. In combining this wetware with an open source operating system Kade has turned himself into something new, a human capable of fully networking his mind with other Nexus users. This potential frontier in evolution, a technology which could unite vast swaths of individuals into a rapturous gestalt of collective understanding and empathy, or in the wrong hands be used for radical thought control, slavery, and domination, attracts the attention of the Department of Homeland Security’s Emerging Risks Division. In a world filled with Chinese clone soldiers, potentially emergent AI, bio-neural hacks to augment any mood or sensation, and human enhancement through nanotechnology, Kade’s discovery of “Nexus 5” leads to his arrest. Therein he must either work with the ERD to bring down another post-human or spend the rest of his life in prison.

Another review here mentions "apocalyptic cults whose followers are infected with god-viruses that make them worship the leaders as messiahs", and that modifying Nexus to give anything more than weak "telepathy" is something that "turns out to be a completely prohibited activity in the USA, where enforcement of a convention against posthuman and transhuman enhancement has spawned a DHS-on-steroids (heh) that can render its arrestees to internment camps without trial."

Amazon shows the cover as silvery, but here's a photo I found of someone's copy where the cover is a shade that might be remembered as pink:

Could it be Afterparty by Daryll Gregory?

It begins in Toronto, in the years after the smart drug revolution. Any high school student with a chemjet and internet connection can download recipes and print drugs, or invent them. A seventeen-year-old street girl finds God through a new brain-altering drug called Numinous, used as a sacrament by a new Church that preys on the underclass. But she is arrested and put into detention, and without the drug, commits suicide.

Lyda Rose, another patient in that detention facility, has a dark secret: she was one of the original scientists who developed the drug. With the help of an ex-government agent and an imaginary, drug-induced doctor, Lyda sets out to find the other three survivors of the five who made the Numinous in a quest to set things right.