Checking for 'City of Lost Souls' on audio is a bit like digging for treasure. It's the fifth book in Cassandra Clare's Mortal Instruments series, and its publishing rights shifted around over the years, so availability depends on your region. The Simon & Schuster Audio version, narrated by Natalie Moore, is the one to look for.
I found mine through Audible a while back, but I've heard people say it sometimes disappears from certain marketplaces. It's definitely on Scribd as part of their subscription catalog, which is a solid, all-you-can-listen option if you're a frequent audiobook user. Your local library is another great route; most use apps like Libby or Hoopla, and you can place a hold for the digital copy. I've had mixed luck with Google Play Books and Apple Books—sometimes they have it, sometimes they don't. It's worth a quick search across all those platforms.
A heads-up: avoid any site that offers a free 'download' without a subscription or library login. Those are almost always pirated, the audio quality is terrible, and it just feels wrong for the author who created this whole Shadowhunter world we love. The official versions have that crisp, professional narration that really brings Clary and Jace's chaotic energy to life, especially during those intense Malachi plot moments.