As you embark upon your publishing journey, an essential consideration is the visual appeal of your work, particularly if you're venturing into genres that rely heavily on illustrations such as children’s books, graphic novels, or certain non-fiction sectors. Hiring an illustrator is no mean feat; it requires strategic planning, meticulous selection, and a keen understanding of your project's needs.

In the realm of publishing, the illustrator plays a vital role, breathing life into the author's words through the visual medium. They contribute significantly to the aesthetic value of the book, thereby impacting its marketability. Hence, hiring the right illustrator is a critical step that could make or break your publishing project.

The process begins with the assessment of your project's requirements. Here, you have to delineate the stylistic and thematic elements that you believe should be embodied in the illustrations. Are you looking for a whimsical style or something more realistic and detailed? Does your project necessitate knowledge of specific cultures or historical periods? These specifications will help narrow down potential candidates and guide your hiring process.

Next, you need to delve into the labyrinth of illustrator portfolios. This task can be daunting given the plethora of talent available, but remember, you're looking for someone who not only matches your stylistic preferences but also aligns with the intended message and tone of your book. Pay attention to their versatility, attention to detail, and their ability to convey complex ideas or emotions visually.

Navigating the economic elements of hiring an illustrator can be likened to a chess game; it's all about making the right moves. Bear in mind that illustrating a book is a time-consuming process, often requiring several iterations before reaching the final product. Hence, it is only fair that illustrators are adequately compensated for their time and skill. However, striking a balance between fair compensation and budget constraints is crucial. In the publishing industry, illustrators might be paid a flat fee, a royalty fee, or a combination of both, which could impact the overall cost of your project.

In terms of contractual agreements, it's essential to ensure that the terms are clear and mutually beneficial. The contract should specify the scope of work, timeline, payment details, and importantly, the rights over the illustrations. These may include reproduction rights, derivative rights, or display and distribution rights. A keen understanding of copyright law is essential here to protect both parties.

In the hiring process, it's also important to consider the illustrator's professional behavior and communication skills. As this is a collaborative endeavor, the illustrator must be able to take criticism, adapt to changes, and communicate effectively and promptly.

Furthermore, let's not overlook the importance of maintaining a harmonious author-illustrator relationship. The dynamics of this relationship often reflect on the quality of the finished product. It's a partnership where both parties should feel valued and inspired.

So, why go through all this trouble to hire the right illustrator? The answer lies in the potent impact illustrations have on storytelling. They intensify the reader's experience, augment the narrative, and often serve as the driving force behind the book's marketing and promotional activities. The right illustrations can captivate your target audience, thereby increasing the probability of your book's success.

To sum up, hiring the right book illustrator is a complex process that requires a strategic approach, a clear understanding of your project's needs, and a fine-tuned balance between creative aspirations and pragmatic constraints. However, the rewards of this laborious process are manifold, potentially culminating in a book that is not only a literary masterpiece but also a visual delight.