The phrase "adding to his series" is correct and usable in written English.
It can be used when referring to the act of contributing additional items or elements to an existing collection or sequence.
Example: "The author is adding to his series of novels with a new installment that explores the protagonist's backstory."
Alternatives: "contributing to his collection" or "expanding his series".
Meanwhile he continued to add to his Sequenza series and to display his orchestral expertise, whether in original works, in arrangements or in such self-arrangements as the Chemins string of Sequenza-based commentaries.
His production of South Pacific, now the standard by which this musical will always being measured, and his uniformly lauded Joe Turner's Come and Gone, have only added to his diverse series of daunting accomplishments.
Herbie Brennan adds to his "Faerie Wars" series with a new book, "The Purple Emperor" (Bloomsbury, $17.95 and £12.99).
Last week he told "white publications" not to write about his music any more, and on Tuesday night, Ezrin was added to his hitlist in a series of tweets.
As political oppression began to impinge upon the daily life of Egyptians, Idrīs added to his authentic visions a series of new and symbolic portrayals of oppression and alienation that encapsulated an entire era in contemporary Arab societies.
His marble and resin furniture is sculptural in nature, as evidenced by the stunning new offerings he's just added to his ongoing Lagoon table series.
Vettel added to his lead in the drivers' series, and is now 36 points ahead of Alonso.
Hales is one of three batsmen ending the summer with a question mark against his name, along with James Vince and Gary Ballance, although added to his struggles during the drawn series with Pakistan is the £1,500 fine he received for storming into the third umpire's room at The Kia Oval to argue a decision.
To further add to his confusion, he encountered a series of islands north of Abaco Island, which looks very similar to the Key West Islands, but he was still over the ocean instead of over Fort Lauderdale.
With the Astros taking a 2-1 lead in the best-of-seven series, Clemens added to his legend.
